Gumtree is still the worst but I had another good one on Ebay a few weeks ago...
I was selling a scanner. Buy It Now price of $100. I also allowed buyers to make offers.
The first offer came in. $10. Naturally I rejected that. The second offer (same guy) $15. I then blocked him from making further offers and in the end he opted to pay the full price of $100 with the Buy It Now option.
Minutes later I get a message asking for a discount: "...I'm on a pension and can't afford this at the price you're selling..." kind of thing. I reply with a simple "Tough tits. If you can't afford it, you shouldn't have said you'll buy it." although not quite as blunt as that.
This was followed up with a request for some free AA batteries. Again I said no but I did offer to chuck in a USB lead instead. This appeared to shut the idiot up and I posted the scanner the next day even though I knew the guy was going to be trouble. I even opted for the tracking and for the parcel to be signed for as I knew the buyer would try and claim the parcel never arrived.
Two days later, as I expected the trouble started. I get a message along the lines of "This is a piece of ****. It doesn't work. I've thrown it in the rubbish. Give me a refund!"
I replied with the clarification that the sale was non-refundable, that the device did work as I had tested it the night before I posted it but it he was truly unhappy I would give him a refund once I had got it back.
Again, he angrily stated that the scanner was a piece of ****, that he'd thrown it away and wanted a refund. Again I said a refund would only be issued if he sent the scanner back. This went on for a few more days but I stopped replying after the second message. He eventually left negative feedback which in all honesty I'd rather have than have to deal further with this numpty.
Negative feedback lasts 12 months, this poor guy is going to be a moron all his life.
