Research notes
The ten-week trap: why vial size is not a billing cycle
Twelve 28-day cycles make 336 days, not 365. That gap is why a 70-day charge recurs more than five times a year, and why dividing it by two and a half understates the annual cost.
A supply period describes how long the dispensed medication lasts. A billing interval describes when the next charge is taken. Programs frequently publish the first and let the reader assume the second, and the assumption is usually wrong in one direction.
When a program bills every 10 weeks, the charge recurs on a 70-day cycle. There are 365.25 days in a year, so the charge recurs 5.21 times. The monthly equivalent is the charge multiplied by 365.25, divided by 12, then divided by 70. For a $199 charge that is about $86.53 a month, not $199 a month and not $79.60.
Our registry records a cadence per offer from the provider page. When the page never states the interval, the record is marked not established and no monthly figure is derived at all.