I also like to do research on some things, if I'm either unsure about the item or the price. There have been many times I've thought about an item, only to find I waited too long and lost out. That's the way the cookie crumbles though. As far as dealers being sneaky, aside from trying to sell empty Jaegermeister bottles for $10, I have never had an issue. I'm in a really small area, and they know me, know I usually know what I'm looking at, and know what it's worth. They will also put things aside, if I really want it. They do this, because I've always been fair with them, paid what they asked- as long as it was in line with reality. Those that are way high, I try to haggle down. If they work with me, I buy a lot from them. They act like their stuff is worth a lot more, I just don't go back.
An amusing story for you- I went to an antiques and gift shop, they were having a big clearance sale. Everything was half off. Going through this big Victorian house turned shop, they had lots of flowery stuff, pillows... basically girly decorative garbage. BUT, outside was this nice cast iron bird bath. Not actually antique, but it was made in that Victorian style. I asked the lady how much she wanted for it. She stammered, and says it wasn't really for sale. I countered with the sign says everything goes, how much? She then says, well... I think I paid $40 for it. I counter with the sign also says everything is half off. Here's $20.
It is sitting out in the front garden