Sounds like a decent deal depends on a few variables, size of the co2 tanks, gauges no gagues..etc..
New 5 lb co2 tank is 50-70 bucks, 20lbs $100 or more, used can be found for less, gauges depend on type, one or two stage …so that's another $20-50 plus, used 5 galloon corney kegs are $20-50, and usually need a new set of gaskets. Not sure what you mean by beer tap heads, I think you are talking about the faucet? They can be anywhere from $20 to 50 new depending on who makes them and what they are made of. (Perlicks IMHO are the only way to go)…as far as the kegarator itself, also depends on condition and age? But over all I would say it sounds ok, I would offer less than what they want and go from there….make sure you know what you are getting… best of luck.