If you are to believe that Reddit is setting the API pricing as high as proposed to eliminate 3rd party apps, rather than to recoup costs of allowing their existence (which I wouldn’t put it past them to lie like that to make it sound more palletteable), then it’s reasonable to believe Apollo’s existence doesn’t cost them 20M$. In fact I’d be surprised if it even costs them the 10M$ figure because Reddit’s reaction implies a number that high must be extortion.
There is the Anno series of games, which are technically RTS games but if I’m honest I find them the most fun when I go out of my way to avoid combat/micromanagement. I’ve only played 1404, 2070, and 2205, 2070 being the best in my opinion, but it has a bad history with DRM so I’d suggest 1404 (known as “Dawn of Discovery” in the US because us americans are afraid of numbers apparently).
Edit: looking at the steam page it looks like they decided to take 1404 down and made a new page where the game is (mostly) unchanged besides requiring you to jump through all the BS hoops that 2070 did, so I’d say if you’re gonna spend money get 1404 on GOG, or if you are willing to do unspeakable things go with 2070.