What kind of work are you doing/what do you need a machine for?
Not sure what your market is like up there but those prices sound kind of steep for machines that age. Good older cheap blades are few and far between, but they can still be found.
If you can get into the 720/730/740 machines series 1 or series 2 machines you'd probably be a little better off. I've got a Series 1 720 that's an early 80's model and its a pretty tough simple machine. I'd steer clear of the Allis Diesel motors (Doubt theres many left at this point). Theres 100 things to check on an old used blade. At that age its more likely than not going to have some significant play somewhere, which just is what it is. Check the front end, see how loose the king pines are, check wheel bearings. Hydraulic cylinder seals, Mouldboard (Has it had the cutting edge worn through into the frog, is the face of the blade cracking anywhere, is it straight, etc.) Do most of the vital gauges work? Anything been unhooked? Trans pressure normal, does it fluctuate. If its a power shift any signs of excessive heat/cooling issues. Are the Hydraulics smooth and have reasonable speed? Has it been getting grease, are fins on the radiator and trans cooler clean? How good are the brakes, leaks at the wheel cylinders, evidence of the master cylinder getting topped off excessively? Is the rubber serviceable, rims rusty and show evidence of calcium chloride.
Paying a mechanic for a once over is well worth it, there's a steep learning curve and if your not able to perform your own repairs, rebuild hydraulic cylinders, etc. a cheap worn out machine is going to cost you as much or more than a decent machine in the long run. I've picked machines up for 10k and put a few grand into them and had a serviceable (read old, ugly, but reliable) machine that made money, but I had time, only put a few hundred hours a year on, and don't mind wrenching on old junk. Down here high teens to 20k is the low end of the price range for something from the late 80's to early 90's that isn't shot. (Dresser, Champion, Older Deeres)
