A price quoted “monthly” is usually a price per calendar month. Sometimes it is not, and the difference is invisible at the point a reader compares two numbers.
Thirteen is not twelve
A seller billing every four weeks charges thirteen times across a year, because fifty-two weeks divides into thirteen four-week periods rather than twelve. That is roughly an eight per cent premium over an identical figure billed by the calendar month, and it never appears on the price tag — the same class of gap that the disclosure scorecard marks sellers on. At this corpus’s median published figure of $179 a month, the thirteenth charge is $179 a year.
21 sellers here record a four-week interval in their own pricing notes. 32 record some non-monthly interval in total, including 3 every week, 2 every eight weeks, 6 every twelve weeks.
The longer intervals cut the other way
Twelve-week billing is the mirror image: fewer, larger charges rather than more, smaller ones. It is not a premium, but it is a commitment, and a reader who stops treatment partway through a quarter has usually already paid for it. Neither interval is dishonest. Both make two published figures non-comparable until the interval is read alongside them, which is why the questions worth asking start with the terms rather than the number.
Reading the interval first
The billing cadence check lists every seller whose own note names an interval, with the charges a year each implies. It is the first thing worth reading on any seller whose figure looks competitive, because a number that turns out to be per four weeks is not the number it appeared to be. For the sellers that publish every rung of a ladder instead, see published dose ladders.
Counts are computed from this site’s own records at build time, most recently read September 2026.