I agree, or at least I wouldn't pay those prices anyway.
"But what can a Stadia customer do if they don't like the prices listed?" - Very soon there'll be heavy competition with cloud gaming services. XCloud, Stadia, PSNow... we know EA are working on a cloud service too. Everyone's going to be trying to get in the ring and there will be price wars. Just not in the next few months.
Stadia may essentially have a monopoly at the moment, but that will change quickly. Then the competition for game prices will start and will be fierce. With Zero barrier for entry (No expensive hardware to buy) these services will have to offer the best price and best performance for their games or people will just buy it on another service. There'll be no problem switching between them on a whim.
True. I see Xcloud making Stadia pretty much irrelevant though. Xcloud is Gamepass but with the added ability to stream to phones and tablets right? That would win easily because there's no need to buy games with Gamepass. Xcloud would be the true Netflix of games. And I would honestly welcome that as a part of the industry.