If they have (access to PS3) I'd suggest to get a very cheep hard copy PS3 version (in UK it's less than £4 now) and then upgrade for free to PS4. This way they'll have a full experience during their "testing" and worst case scenario they'd "waste" a fraction of the cost of the full PS4 game. Heck - if I'd want to recruite a couple of friends I'd buy them the game myself at this price and send them invite code as well ;)
