well, look at it this way, if you buy it all and just toss the tubing and regulator (which I would), then you are still getting an ok price for the kegs and tank.
I suppose it depends on the area, but I have absolutely no problem selling used corny kegs for $30. The tank looks good, and the regulator looks like the Cornelius regulator I have right now. Very reliable.
I would test the regulator and if it's good, use it.
+1 on not the greatest deal ever but it is definatley a fair price. i know when i bought all my stuff seperatly i probably paid more than that. if i was eager to get kegging i would buy it. a year or so from now you will see the same setup for $100 or $125 and you wont kick yourself in the a$$ for paying $150 trust me. oh and if all the regulator has been used for is beer gas i think you are in good shape the set of gauges i bought is forth gen brewer stuff and it works fine for me