Half of those games have been cheap on Steam and other key sellers. Most of them aren't all that impressive unless you've been neglecting them for years or are starting out your PC collection. GMG has made mini bundles of those games for years.
I own majority of those games so this offer isn't for me but as I mentioned, if you're starting out or missing some of them, go for it.
Mind you, Steam would need the approval of those games' publishers to even give them away with any particular purchase, and those pubs would likely much prefer users spent for those titles than however much Valve would cover in return.
Even GOG only offered 2 or 3 games only per user for reaching a specific amount spent on their store in prior sales.