I hate it when people see a $100+ price-tag for a lifetime subscription and complain. A OTP is literally a user that cannot be charged again, and if lemmy keeps growing, it will provide value for many years.
I used sync pro for almost 10 years and paid something like $5 for it, such pricing is unsustainable for the developer and I totally understand the subscription model
Dude has the best app for lemmy and provides a good boost to the ecosystem which benefits all. Development time costs (a lot) of money and the dev has every right to charge what he wants.