How much should I expect to pay.....
for a VERY lightly used jekyll 500 '02-'03?
Ride your bicycle(s)!
The general rule of thumb is...
after one year expect to pay about half of normal retail, and then subtract about $100 for each year after that. The main reason that mountain bikes lose so much value in their first year is that warranties are non-transferrable, so you, as the buyer of a used bike, get no coverage. Personally I'd prefer a 5 year, transferrable warranty on frames to a lifetime non-transferrable one.
"The question before the human race is, whether the God of nature shall govern the world by his own laws, or whether priests and kings shall rule by fictitious miracles."
John Adams to Thomas Jefferson, 1815