The
L4150 started production in the early '80s and was sold thru 1990. It's official "year" was the year it was first sold at retail. They gave it a couple minimal changes and a new model number (
L4850) starting in 1991. The last L4850s sold around 1997. These tractors are beefy, strong, beautifully over-built, designed to last forever. That said, however, 2500 hours is long enough that if a machine has been abused, it shows - especially if it has a backhoe.
The money on these rigs is in the hydraulic shuttle (if it has it) and in the loader and backhoe hydraulics. Test the backhoe for down force - with the stabilizers down (back end of the tractor lifted off the ground) see if the backhoe will lift the back end still higher to shift the whole back end of the tractor sideways. If not, then the pump is worn ($$$). Same thing with the loader - it should be able to lift the front axle off the ground with the back of the tractor already up on the stabilizers (backhoe tucked in so it's a minimal counterweight). If it can't the machine has hydraulic wear that probably extends to all the piston seals, control valve spools, transmission shuttle valves and clutch packs etc, etc and is likely to be a constant hole in your checkbook. My 2 cents. I have one of these machines - it has 1100 hours and is in very nice shape (tight). But I've seen some for sale that are loose. It all depends on how it's been used and if the fluid has been changed out when it gets dirty.
A fresh tight rig with strong pumps, good rubber, tight valves, etc,etc. might be worth $22k. But a worn one might only be worth half of that. If you can hire a TLB mechanic to go look at it with you it might be money wisely spent.