Doesn't this UX guy know what he's worth? Isn't it on his head to decide where he's going to work, at what pay? Of course his belief in this founder's dedication plays into that, he's trying to find a job that'll last. But let the UX guy decide what he needs to take, from whom. You don't know him, what motivates him. If he's even -interested- in work at such a startup, money likely isn't what he's running for.