Before buying, I'd want to give it a try and make sure there are no leaks in the valve assembly and every cylinder works properly under load. The most common thing that happens and has been reported by several members is the spools, the rods that go up and down in the various valve control blocks, can get some rust on them. The spools are sealed by rubber o-rings with nylon backup washers at the top and bottom of the valve block. The rust can tear apart the o-rings and then leak hyd fluid. Other than obvious visual damage, the pivot pins and bushings for the boom, dipperstick, and bucket can wear but are replaceable. An easy fix if replaced before the wear goes into the actual pivot housings. I've replaced my boom and dipperstick pins and bushings with about 100 hours of use and they were always greased well. I spray the spools with fluid film when not using/storing the bh. Cylinder seals can go but this is less common. Hard to say if it's worth $1200 less without seeing and trying. Pivot pins and bushings aren't that expensive but valve block parts can be. If hardly used, then probably a good buy. Didn't say the above to sway you. The 23 just needs checked over.
