Both unreal and unity have costs involved in other departments, and may have features disabled or add on modules and other hidden costs.Unity pro is over $1000 and add on modules costs some serious additional money, extra media also costs some serious bucks.So people's eyes glaze over when they read free, they don't read the fine print........
GameGuru is 20 bucks and that is the extend you need to pay, no hidden or additional costs, same applies to store content, what you see is what you pay.It really can't be any simpler.You also forgetting there is other engine that you need to pay for, leadworks, the rpg maker, gamestudio A8, axis game factory, ect, ect, Gameguru isn't the exception here for having a paid engine.Free engines is hardly the norm, having 3 big engines having free options, it doesn't mean every one should follow suite, because they are doing it.
Each engine, has their own features, content, additional modules, ect ect.Game guru punts ease of use, and any one can make a game in minutes, which none of the other engine can say.What you see is what you get, not much right now, give it a few months, and people will be happy to spend 20 dollars on some thing without, hidden costs.
Win7 pro, Intel 2500K @3.7ghz 660GTX 8gig ram 16tb HDD