For a brand new, AAA game, it's $60 with a smattering of $50's and one $70. There are plenty of brand new games that come out for less, though. They aren't as high quality but they can server niche gaming tastes. Wildermyth and The Forgotten City are both recent examples of very good games that only cost $25.
(I'm ignoring "free to play" games. You never know how much those things will really cost you.)
The good thing about Game Pass is that I'm trying out games I never would have tried before because it doesn't cost me any more to play as many games as I want on there.
The old OnLive service was like that, too. It only let you play for 30 minutes, but there was also 0 installation process. I found Just Cause 2 that way!