Check out edmunds. I assumed it had all options except sport suspension, is in clean condition and it returned trade-in, private party, and dealer retail prices of $10.7, $12.1, and $13.9, respectively. Notable is that with the low miles this one gets an additional $660 of value- this is not real value, IMHO, so you are looking at adjusted values of $10, $11.5, and $13.2. If buying from a dealer, which in many states has to warrant the vehicle for 90 days, you should be paying somewhere between private party and dealer, say, $12-12.5. If buying from a private party, you should be paying between the trade-in or wholesale value and private party, or $10.5-11. Don't overpay- you have lots of options. Off-lease Volvos are plentiful and reasonably priced. For example, I bought my loaded '99 T5 with 33K for $20.8 one year ago and it came with a set of mounted snows- 3 years old for 55% of original sticker.

Things to look for are typical 850 issues like a/c, transmission, swaybar endlinks, upper torque rod bushing, etc. The first two could be pricey, the others are fairly minor.