The fossify apps are legit, I use them daily.
This is the same or similar situation as OpenOffice → LibreOffice or OwnCloud → NextCloud (and to a lesser extent but more similar scenario, Audacity → Tenacity or various other forks).
This is what true open source looks like in action.
Everything is artificially inflated by 1.7x to 2.4x ever since covid. The inflation you are seeing is not real inflation but rather manufactured by those in high-up positions at most fortune-500 companies.