That only applies for steam keys afaik. You can not sell your steam keys cheaper anywhere else, since steam is on the hook for the cost and services. That is fairly logical.
A dev can charge whatever if they deal with all that themself on their own webpage forinstance.
edit: had a hrd time finding the video i knew i had seen this on : https://v.redd.it/xnl8xyki4h5d1/DASH_1080.mp4
What is wrong with your system that requires disabeling updates?
Been running debian stable on a few hundred servers for 25 ish years.
And I always install and enable unattended upgrades. And it have never been a problem. Not even once.