If I remember prices when I looked at Home Depot I figured out that I could buy two planes on ebay for the cost of one at Home Depot. I figured this meant if I happened to get a lemon from ebay and had to buy two just to refurbish one I was still getting a much better plan for about the same cost.
I spent about 2-3 weeks looking on ebay before buying. The first week I really just wanted to get a feel for prices and flow of listings. Then the second week I started putting in bids but very low ones. I always made sure there were some good pictures up on the site so I could see the general condition of the tool. If it seemed like there might be a problem refurbishing it I just held off and looked at other listings. Also don’t be afraid to send an offer on non-bid listings. I was able to get a full like 9 set of 750 chisels for around $80 just because I was willing to submit an offer and take a chance. Take your time getting to know ebay and what type of tools are listed. Determine your highest price your willing to pay and for what quality, then stick to it. Also remember, there will always be a new listing that will come up next week. If you got outbid on the tool you really wanted for the price you really wanted don’t be to heartbroken over it. Better to stick to your preplanned price and bid again tomorrow than wake up the next day and regret how much you spent. Like I said, the hardest thing for me to remember, was that there will always be another listing. If I don’t win a bid today, I’ll have another chance tomorrow.