Sebastian LaVinePro tip to vendors at conventions: If you seem annoyed by the minimum effort required to sell something to me, I'm probably not going to buy something from you
Yesterday at #RetroGameCon in Syracuse I was a stand which among other things had some old "PSP Go"s. I asked to see them, see if they could hold a charge, try button quality etc. They seemed kinda annoyed at me wanting to know whether the product they were selling me worked. That, plus the buttons feeling kinda gummy, led me to not buy it.
Later at another booth, I asked if they had a PS Vita. They did, and pulled it out and showed it to me and let me play with it a bit. They were knowledgeable about the details and were upbeat and happy I was interested. I purchased it and a game for trade-in + $100 cash. It was a better product too, but I didn't really go in there looking to buy a PS Vita, and if the vendor wasn't happy to talk to me then I probably wouldn't have ended up buying it!