I rarely look things up on ebay when i'm at a sale, but if I want to, I will still only do it if it's priced a little higher than I generally like to pay and if my wife is with me and she's still browsing the sale. If she finishes and I haven't finished looking it up, I usually just leave it. My service tends to be a little slow in some of the areas that I yard sale though, so I just take educated guesses most of the time.
This year I have a searchable price list on my phone so I can look things up very very quickly. I'm hoping this will help me out when I see games I'm unfamiliar with. Two more days for my season to really get started.