kbt, I made a deal to buy a B2710 and trade-in my 1995 B7100HSD with just under 500 hours a year ago this month. I had a front end loader on mine instead of a belly mower and the dealer gave me an honest $8,000 for it (don't know what he turned around and sold it for).
The lowest price that I've seen on a B7100HSD 4wd with mid-mower and around 200 hours (show room new appearance) was around $5500 during the summer of '98. That one didn't last long. I've seen asking prices as high as $9000 lately, but don't know how long they lasted.
You didn't indicate whether you tractor is a B7100HSE (2wd) or a B7100HSD (4wd). The price also depends upon which part of the country you live in. To generalize, I have found that 4wd compact tractors are much more popular (and higher priced) in the hillier terrains whereas in the flat terrain parts of the country the compact tractors are not nearly as popular as the "mondo" tractors are. I recommend that you try www.traderonline.com which is a nationwide classified advertising magazine. You can do name searches (such as "B7100") and get an idea of what they are selling for around the country. If you wanted to compare against a "New" price compare it with the B7300 which was its replacement (nearly the same specs).