I would say a core pump should be worth maybe $200-300. I say that because when I was buying up sitting M130 engines around Holland and Germany, I would typically get a complete engine (with alternator, started, FI pump, exhaust and intake manifolds, power steering pump - the lot) for maybe EUR 500 a piece.
More importantly, these pumps are quite robust. If you just make sure all is free (the control rod, the warm running thermostat/tower etc) then chances are good this pump will work just fine.
I have maybe 12 of these FI pumps sitting just like the one you are looking at. One day I will examine, clean, check etc them all, then search for a proper service place that can bench test each one, so I know what I have. Or, I just may test each one right on my own car for real-life testing.