Domains pushed at Enom need 7 days between two account pushes. As in they can't push the domain back for 7 days after you pushed the domain to them.
End users cannot be treated the same way as domainers, even with them it sometimes takes time for resolution, don't be impatient.
I'd recommend that you explain to them why the domain is worth $495, also explain to them that once they have accepted the terms and the domain, the deal is binding.
If they still don't come through w/ the payment, just accept the domain back, threats are going to get you nowhere.
Spoiling their name might give you some satisfaction, not much else, it will also ensure that this end user and anyone they know will hear about this bad experience, making it that much tougher for that group of people to accept similar offers in the future. Plus they might just come after you legally for slander, though I doubt it, why open yourself up to problems unnecessarily.
This is just how I would handle it, you might prefer a different method, but think about the consequences of such actions before you indulge in maligning anyone for a failed deal. The amount of time wasted on this could be constructively spent on approaching the next end user. Jmho.
