Hey Joe,
In all honesty, that's beside the point. If I had a penny for all of the bad reviews our products (and our company) have gotten, I'd be a rich man. But that's the nature of being in business online. Like it or not, people WILL review your business practices, your products, etc. This is no different than the scores of people that leave poor reviews on Amazon.
The difference is, your company is still (seemingly) in a position to be this close to its customer base, so it feels a bit more personal for you.
What you want (need) to do is safeguard your business's reputation by valuing IT more than the few bucks you would've lost over a possible technical glitch. In MY opinion, your offer was no-where near reasonable. His was. He gets 1/3 of the deal he would've had originally and You keep 2/3 of that inventory at your higher price AS WELL as a returning customer (not to mention the potential sales you lose from one bad review).
If it truly was business, you could've made a wiser business decision and not taken his posts personally.
Cheers and good luck.
PS.
I always remember this when it comes to reviews and the customer experience. "It's always easier to destroy, than it is to create."