Does he like the cue he's shooting now?
Before blowing $500 he should be sure he's going to like shooting with it, otherwise it's just a pretty piece of wood, IMO. Might ask him basic things such as does he like a stiff/softer hit, more/less feedback, etc. If he's not sure maybe he could compare his taste to a production cue. For example if he liked he way a Meucci Original hit, then he probably likes a softer hit with above average feedback. If he likes a J. Pechauer then he likes a firmer or crisper hit but still not as stiff as say a Schon.
I am not an expert on custom cues, but I know from reading some reviews which customs I believe I would like or which cuemakers would make the cue to my personal tastes.
Like I said, just my opinion, but to me $500 is a lot of money.