They don't need to recoup their investments in discovery and regulatory approval.

What do we believe the discovery pathway was? Billions of dollars spent by heady businessmen with a keen eye for the molecules of interest? Hardly:

https://www.pnas.org/doi/10.1073/pnas.2415550121

And this type of drug lends itself to some of the least expensive trials you can hope for. The dosage level, expected dosing period, and measurement of outcomes are all uniquely well suited to inexpensive study. The trials were also exceedingly fast and quickly broke off into testing for all kinds of conditions such as Parkinsons but for the core case of weight loss it was as easy as it gets.