Valve will take the cut from the sale no matter what of course, but the DRM and even the in-game Steamworks integration is actually optional. You can publish DRM-free files on Steam which do not require Steam to run at all if you want. People might get grouchy if you skip achievements and save sync or whatever, though.

ETA: https://www.pcgamingwiki.com/wiki/The_big_list_of_DRM-free_games_on_Steam

And to further clarify, you do not need to eschew achievements and that other stuff if you want your game to work without steam. You can make your game check to see if steamworks is working and then provide those services if if available.

I hardly deal with online verification. I travel a lot and have a laptop with singleplayer games I downloaded through Steam and play them with no internet connection whatsoever all the time