Another way of looking at this is, why didn't you just offer him the asking price? Let me put words in your mouth, "What's wrong with a little negotiating?" Nothing, and that's probably why the seller countered.
There should be a "Rant" category...
...but there isn't , so here goes. Someone listed a piece of gear, with their asking price. The ad specifically said to "make a fair offer". So I did, just 10% below asking. He declined my offer and countered....with his original asking price! In dollars and cents, there wasn't really much difference, but it rubbed me the wrong way so much that I moved on. Am I being unreasonable? Discuss.