Three billing structures dominate this market, and all three share one property: they move money out of the figure a comparison page reads. A prepay tier averaged into a monthly rate, a four-week cycle labeled “/month”, and a mandatory membership billed beside the medication. None of them is concealed. Each one is disclosed somewhere on the seller’s own site, and each one is missing from the number printed next to the buy button.
What the roster records
Across 477 sellers and 1,040 published price rows, 66 sellers carry at least one arithmetic correction, filed as 157 entries. Applying them raises 117 rows across 54 sellers by a median of $50 a month — a multiplier of 1.25, and $600 over a year. A further 36 rows across 14 sellers lose their price altogether, because the seller publishes a mandatory charge without publishing its amount, and no payable figure can be computed at all.
Those corrections are arithmetic on two figures the seller publishes, not a walked checkout, and the methodology keeps that distinction rather than promoting one state into the other. Where the seller’s published number itself changed, that is recorded separately — 29 rows here fell rather than rose, because the price was cut.
The three structures are not worth the same
Sorting the corrections by the structure named in their own arithmetic gives three very different magnitudes. A short cycle — a four-week term, or a weekly rate, presented as a month — appears in 50 entries across 23 sellers and is worth a median of $17.33 a month, an uplift of 8.5%. That is the structure with the best claim to being an accident of arithmetic rather than a pricing decision: thirteen four-week fills land in a calendar year, not twelve, and 8.3% is exactly what that costs.
A fee charged outside the medication price appears in 35 entries across 16 sellers and is worth a median of $84 a month — an uplift of 40.9%, nearly five times the short-cycle figure. Ten of those sellers name a recurring mandatory fee in their own copy, and those named figures run from $25 to $125 a month. A prepay rung advertised as a monthly rate appears in 15 entries across 6 sellers and is worth a median of $100 a month, an uplift of 40.2%.
So the structure that looks most like sloppiness costs least, and the two that require a deliberate choice about what to put on the card cost roughly five times as much each. The mechanics of a membership charged on its own cadence — monthly, annual, or once at signup — are worked into a single comparable figure in the annual-cost article.
The structures also stack, which is why the largest single corrections in this file are not the largest single fees. A seller billing a four-week cycle and charging a membership beside it applies 8.3% to the medication figure and then adds the fee to the result, and a seller whose advertised rate is a twelve-month prepay average is quoting a number that no month-to-month buyer is ever charged. The largest multiplier in the file is that combination rather than any single fee: a headline of $95 that resolves to $244 once the prepay average is replaced with the four-week plan and the four-week plan is converted to a calendar month — 2.6 times the advertised figure.
The correction is largest where the price is smallest
Split the 117 raised rows into quartiles by the figure their seller advertised, and the uplift runs backwards against the headline. Rows advertised between $59 and $149 gain a median of 50.1%. Rows between $149 and $199 gain 29.4%. Rows between $199 and $249 gain 18.3%, and rows above $249 gain 19.7%. The cheapest quartile carries two and a half times the correction of the dearest.
That is the finding, and it is the opposite of a rounding artifact. A seller charging $99 and a seller charging $299 are not making the same kind of mistake in the same proportion; the low figure is more often the one that leaves something out, because the low figure is the one doing work on a comparison page. Twenty-nine rows advertised under $150 land at or above $150 once the arithmetic is done, and 41 rows advertised under $200 land at or above $200 — each one crossing the threshold a board or a filter is likely to be sorted on, and many of them crossing the one a price-capped board is built around.
The market average is nearly blind to all of it
Here is the part that should complicate any use of a summary statistic. Across the compounded semaglutide injection field, the median advertised figure is $175 over 459 rows. After every correction is applied the median is $179 over 446 rows — the thirteen rows that lost a price having dropped out. For compounded tirzepatide injection the median moves from $240 over 415 rows to $249 over 401.
Four dollars and nine dollars. A market-level figure absorbs a defect that costs an individual buyer a median of $600 a year, because the affected rows are a minority of a large field and a median is designed not to notice a minority. Anyone reading a category average as evidence that the category is priced honestly is reading a statistic that cannot answer the question. The full distribution behind those medians, and what else moves a number that size, is in the price-variation article.
A prepay term is a bet on persistence
The commercial logic of a twelve-month rung is that the buyer trades flexibility for a lower rate. What the published persistence data says about that trade is unflattering. Among 15,811 commercially insured US adults who started semaglutide for weight management between June 2021 and December 2023, nearly one-half — 46% — had discontinued by the fifth month, with a similar 48% among those starting after supply stabilized.[1]
And discontinuation tracked cost in the direction that matters here. Rates rose from 41% in the lowest copayment quintile ($1 to $54 a month) to 51% in the highest ($161 to $1,460 a month), with higher discontinuation also associated with lower household income and education.[1] A prepay discount is therefore aimed precisely at the buyers most sensitive to price, who are the buyers least likely to still be taking the drug when the term ends. The rung is priced for a year of persistence that, in the best-measured cohort available, most people do not have.
That cohort was insured, on the approved single-dose pen product, and paying a copayment rather than a cash rate, so it is a bound rather than a forecast for a cash-pay compounded buyer. It is the closest published measurement to the question, and it points one way. How the two payment routes compare is in the insurance article.
When the fee is the only number published
Twenty-four rows in this roster publish a figure that is not a medication price at all: a care membership, a program start fee, a consultation charge, or a monthly medical fee, with the drug billed separately and priced nowhere. Those rows reach a comparison surface looking like a monthly cost because they are a monthly cost — of something other than the medicine.
A related shape is worse, and it is why 36 rows here carry no price. A seller states that enrollment in a program is required, and declines to publish what the program costs. Every number on that page is then conditional on an unpublished one, and no comparable figure exists. The honest output is a blank rather than the unconditional figure, and anything a reader or a seller finds wrong with one of them lands in the corrections log.
What this does not establish
Coverage is not census. Eighty-four of the 477 sellers here have been adjudicated on this question — 66 corrected and 18 examined and found to need no correction, including sellers whose published figure already includes a mandatory fee and sellers who state in their own copy that no fee exists. The other 393 have not been individually examined, and the absence of a correction on a row is an absence of examination rather than a finding that nothing is owed on top.
Nor does any of this describe the product. Compounded drugs are not FDA-approved, which means the agency does not verify their safety, effectiveness or quality before they are marketed.[2] A secret-shopper study of 75 weight-loss clinics and medical spas in two states, conducted after the semaglutide and tirzepatide shortages ended, traced their supply to 23 compounding facilities, of which 4 of 21 were not licensed to perform sterile compounding and 3 of 22 had faced state-level disciplinary action.[3] None of that correlates with a billing structure, and a seller with clean arithmetic has told you nothing about its pharmacy.
What the arithmetic does license is a single question at checkout: what is the total charge in month two, and how many days does it cover. A seller that answers both in writing has published a price. One that answers neither has published a headline. Running a specific quote through the cost calculator turns the answer into an annual figure, and the sellers that hold one rate across every dose are collected on the flat-pricing board.