I'm not an IMP mechanic, nor do I play one on TV. BUT
just from the looks of it:
tracks, bogies, drivers,bearings $4k?
brake bands, cylinders, lines, fluids $1500
Would bet this cat needs all of above.
IF engine starts (comparable ) $7K - $5.5K = $1.5 K
No engine, or unknown: subtract $3.5 K
Owner should pay about $2K to have it hauled off.
OK, know that isn't going to happen...
If you want a chassis to rebuild, I'd offer 2.5K and dicker up to your choke point.
There are folks here who would argue with me, but a planning number for a small cat (non-tucker) is $20K to get running right. The lower the initial cost the higher the refurb, and vice versa. There are certainly cats that have been had for a song, but many more that in the long run cost more.
This assumes you do work, have tools, knowledge to do the work yourself.
CT