Another idea which may interest some people is that there used to be a button on EBay to generate an RSS feed from a query. That button went away some time ago but the feeds still work if you enter them directly into your feed manager. I used to have feeds for all the coins I was looking for. I staggered the times they downloaded and had them fire once a day. That way I never missed an auction. For a long time I was also doing the same for completed auctions. I had intended to write a routine to read these feeds from my hard drive and find the trends in the average sale price but other things got in the way and I never did it.