Yikes... Not a great price. I'd put a fully grown yellow from Hawaii at around $300 - $400, but $660 sight unseen and unquarantined would be a pass for me. They used to be 30$ before the ban, basically on the level of a clownfish or gramma. It would also be super easy for them to send an aquacultured one instead, most people wouldn't know the difference. Try Dr Reef or the BIOTA website itself if you want good pricing.
$500-$600 Just sounded totally insane for me. Trying to price one and have no idea what to ask for. Bough it as a tiny one and i think that costed me around $120 almost 2 years ago.