Shifty fuckers. Years ago I bought a Mac app, today the developer upgraded my account – allegedly at random – to Pro for one year without charge, with charging of USD$99 pa to commence Feb 28, 2020.
Only ever bought one app from them in 2011, now that app can be accessed via the Setapp subscription.

I have permanently deleted the account & any applicable software licences.

The "benefits" of having a Pro account?
1: Having a direct email line to the CEO.2: Having a free one-hour online discussion with an app developer.3: Future access to developers at a "discounted" rate of USD$75 per hour.

Costs outweigh any benefits, not participating in that business model.