Do I pass up a sale out of spite?

Selling item for $700 (cost me nothing, all profit). It's brand new and sells retail for ~ $900 (scientific equipment). Buyer offered me $200 (super lowball) at first, I declined. Then $300, I declined. Then $560 and I countered $660. They countered $600 and I declined. They are out of offers now and messaged me that they do it for $660 and need it ASAP.

It's a decent amount of money but buyers like this piss me off. This is just a hobby for me and I don't really need the money. I think I'll tell them to buy elsewhere, ban them from buying from me and increase the price in case they try buying it from a different account. Looks like it is out of stock from where it is typically bought from so they're probably desperate.

***UPDATE***

A couple hours after getting their message I raised the price to $900. A couple hours later I blocked them. A couple hours after that I deleted the listing. I'll relist in a couple weeks. FAFO.

More info: the $900 retail price is approximate. Most scientific suppliers (VWR, Fisher) have contract pricing with their customers and the bigger you are the higher your discount. So, it may even cost them $1100 for this item if they are small (which they probably are). And, I just checked and this item has been discontinued so it is not even available in retail anymore.