They aren't long term contracts and the host gets a bit of exposure doing something they can get a kick out of.I have no idea who this guy is, so I couldn't care less that he's hosting Raw. Unless Brock Lesnar showed up to give him an F-5 or something, but disappointingly enough, Brock isn't even scheduled to be there next week.
Honestly though, if WWE is trying to cut back on money so much, why bother paying these random celebrities to host Raw?
He wants to do it, so I can't imagine his price would be too high. If it gets more eyes on the product, he'll be worth more than any (small name) contracted talent they may have.