As for costs, the lost sales of something like Halo will be millions. Who's going to spend $60 (giving MS $40+) to buy Halo when they can use Game Pass and play it? If those same people were going to buy Crackdown and Sea Of Thieves, that's millions of people not giving MS $120 because they are using the service. That's a lot of wonga! I also don't see why the game being in Game Pass keeps the interest beyond the first two weeks. If the game has longevity, it'll grow and not need a Game Pass incentive to get people to play it (Destiny, Diablo 3). If it's a short lived adventure, it'll peak and fizzle. Those short games make their money by selling at full price.
I get where you are going with that in particular, but you're looking from the viewpoint of the risks involved with game pass. As opposed to, say what the benefits would be. If the benefits outweigh the risk postively enough to provide value for both the consumers and the company then we can assume this is why they proceeded.
There are several concerns that are real, and will likely play out. The main one, being what you wrote, try and 'bye' for $10 which you and many folks have brought up.
The opposing view is this: the hardest part for games in general, is barrier to entry. Getting people to even try your game is tough enough. Getting people to play with you is extremely expensive.
So two fold the game pass solves 2 problems:
a) Groups of friends with gamepass all have the same titles and library, that can as a group move from to game, and play whatever they want as a group. This is something that has been the case, for me for a 1 off day to play basketball say around NBA finals season is something I would never do because I don't pay $80 dollars x 8 people for the week of NBA finals. But now I can
b) Conversely with developers, it's impossible to get people to try your game because of barrier to entry, perhaps your marketing fell through, or perhaps you don't think your friends will try it out. Too much pressure on that barrier to entry to 'try' things. And so developers from this because many games today require participation in large volumes to be successful.
Having resolved those two major issues the only 2 remaining is for Microsoft:
a) How does MS profit from this, well the answer is simple. If the game pass revenue surpass traditional revenues, than it's certain more successful than if they didn't have it on game pass.
b) How does MS continually beef up game pass with more content. Game pass will have to follow in netflix's model. They'll need tons of original and 'fresh' programming to keep their audiences subscribing. And of course, there is always the idea that people would be comfortable enough to just let their subscriptions continue on. Because when you have parties, or guests, or family members, or sharing etc. There are all sorts of reasons to keep subscribed. There are many folks who subscribe to the gym and they never go. And gyms are specifically looking to sign these types of people up all the time.
Definitely an expensive move from MS intended to grow the service. I think it's intended as a loss-leader to try and establish a new business model. If Game Pass includes Play Anywhere on PC for the same games, it's quite obvious what the intention is.
Perhaps? We'll know more by E3 if it's a loss leader or not. But the intentions are to broaden the service for sure. Its' one thing to be Play Anywhere on PC. It's entirely another to be able ot stream your game library to any device. Something PS Now does not offer. They only offer you their streaming catalog.