Not sure if you already accounted for this, but the monthly subscription only includes a subset of their catalog. For any game outside of that you’ll need to pay for the subscription plus purchase the game.
So yes, if the game(s) you want to play one of the included games and the service goes bust you don’t lose much. If you purchased a title and service goes bust then you likely lost that money.
$10/mo * 12 = $120/yr and still paying $60/game for AAA. Alternatively, there is supposed to be a "basic" option coming in 2020 with no subscription fee where you just pay for each game but then what happens when Google gives Stadia the axe? Will users be able to claim licenses or local copies of games they paid for?
As opposed to paying $60/yr for PS Plus + $60/game for PS4 or next gen PS5?
The basic version is also free, which is something Sony isn't going to be able to offer me. But with Stadia I can play on my TV, on my desktop, on the go, etc.
I buy most of my games digitally whether or PSN or Steam. If either of those go out of business, I'm pretty much SOL. I don't see Google allowing you to claim your license for local copies as the Stadia hardware is specialized and custom, not something you can emulate easily outside of it's infrastructure, but that's a risk I'm willing to take.
So yes, if the game(s) you want to play one of the included games and the service goes bust you don’t lose much. If you purchased a title and service goes bust then you likely lost that money.