Im not sure for Hell Let Loose, but Chivalry 2 is a Unreal game and all unreal games come with a server.exe that works by default and works through direct IP connection. It would cost them 0 and im sure the game could just host servers with the normal client build like all unreal engine games do by default.
Just no. There's zero reason (other than greed as you can rent your own server) as to why you can't run your own server with Chivalry 2, likely no reason for Hell Let Loose either. I ran a Chivarly 1 server for years, its just an unreal game with a server browser, its not an mmo or pubg like matchmaking style that requires more infrastructure to run. And even if you did that, you could still allow people to run their own private servers, just have an old style server browser, which comes out of the box with engines like Unreal.