Comment by pertinhower

Absolutely. In the 2000s the Unreal Engine had a price tag of half a million dollars up-front plus royalties (I don't remember the percentage) on the back end. That these companies are giving their engines—even their source code—away essentially for free indicates either that (1) engine sales was never a very lucrative line of business or that (2) the promise of establishing your technology as a defacto game engine standard—the Panavision of games—is even more appealing than immediate revenue.