Generally speaking, in european sports you get payed what you're worth. Your age doesn't really factor into your salary. So, if he's as big a talent as it seems, I'm 100% sure he could make more money in the KHL then the AHL side of a two-way entry level contract.
That said, I think most people would agree that the US/Canada is a better place to live then most parts of Russia. Add the fact that there's still more money to be made in the NHL, and the fact that the NHL is hands down the best league in the world, and there should be plenty of motivation to come over the pond.
I actually wasn't aware they had a salary cap in the KHL untill just now, never heard of that in any european sport before, but it seems they do.. (Some soft of softcap untill this year, where they introduced a hardcap of $36.5M + one player from the NHL outside of the cap.) I guess they are modelling the KHL after the NHL. I'm sure they don't have two-way contracts similar to the NHL though. Frankly I don't even understand why the NHLPA accepts the concept of the two-way contracts.. seems completely retarded to me. And I have no problems accepting the reasoning behind staying in the KHL for a solid paycheck, instead of coming to the NHL on a risky two-way contract.