The program is called "Extended Security Updates for Windows 7", and the fee isn't exorbitant, but it's not necessarily cheap either. For 2020 it's $25 / PC, rising to $50 / PC for 2021, and $100 / PC for 2022. There's background here: https://docs.microsoft.com/en-us/lifecycle/faq/extended-secu...

Background: I have a Customer who needed to maintain Windows 7 support for a legacy application on a single computer. For $175 to get 3 more years out of a paid-for critical application it was a "no-brainer" (and 3 more years to figure out a replacement strategy). Obviously, not all situations will be as simple.