I bought mine in NY with 130,000 miles original everything on it with a very small amount of rust on the floor pans for $2,500. NY prices are cheaper than the south. When I moved to GA, it sold for $3,200. Hope that helps some. Depends on miles, maintenance, rust and the buyer.
YJs can run anywhere from $3K to $8K. Less if they are rust buckets or have issues. More if they are heavily modified and done correctly. However, I don't see many higher than that - I think most people would rather build their own than just buy a built Jeep. That's just what I've seen. Average price is right in the middle at $4-5K. The price is location dependent too. Condition, miles, etc, all factor heavily into it.
Check Auto Trader, Craigslist and eBay for your area to get a feel for the prices of similar YJs. 2.5Ls will be less expensive - probably $1000 or so.
1995 YJ, 4.0L, AX15, 3" susp lift; Lock Right in Dana 30; 8.8 w/ARB; Flat Tummy Tuck, 1" Daystar BL; 1" MORE MML; 35" MT/r Tires;
I checked my NADA book. and the low retail price is $2,225, and the average retail price is $3,975. You wont get a high book price on a 91 unless its in pristine showroom condition.
Those prices are a national average. Some spots in the U.S. are higher, and others are lower.
Like Stan said, check craig's list for prices in your area. A good rough average to go by is $500/yr difference. In other words if a 94 is selling or sold for $4000, then a 91 which is 3 yrs older would sell for $2500.
'87 YJ, 4.2L built and bored, 8.5" of lift, 8.8 rear, AX15/NP 231, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...