>Then why have it in the first place?

The inconvenience/effort is probably the point, likely to discourage people who aren't willing to put at least that much effort.

>and hope I don't get banned for using unauthentic testers.

I doubt Google cares about this, since they let apps for these testing groups into play store. Those apps organize people into groups, provide play store links, and buttons to open other people's apps, so all you do is just open and close each app once a day.

Since this takes like 30 minutes total over 14 days, I'd rather do that than pay $100 forever since I'm not made of money and it's less time than it would take me to earn $100 at my job even once.