I have a 6" Speeco auger & my 12" Speeco auger ran off with my old tractor & PHD. I paid under $200 for the 12" auger & ended up replacing it with a $375 Pengo auger. The Speeco did about 200 holes & needed new teeth ($15 each, requires 2). Teeth are a wear item, so no suprise there. The holes to mount the auger to the PHD were tearing & wallering out a bit. Still usable, but wearing out a bit. I'd have had to weld on some reinforcemnt if I were going to keep it. I'd recomend it for a homeowner unit for a couple acres of fencing.
I upgraded to the Pengo because I do side work with my tractor, including a decent number of post holes. The Pengo is a MUCH beefier auger, lots more steel all over, reinforcing collar at the mount point, multiple replacement tooth options (basic teeth are $5 each, requires 4, so cheaper than the Speeco).
Really PHDs don't wear out. Generally something jams & there is a catastrophic failure. So if everything is straight & there is lube in the gearbox it should be good to go. Used augers are probably worth $100 each as long as there isn't any wear on the bottom because they didn't replace the teeth appropriately when they wore down.
When looking to replace my old 3pt PHD I was looking to pay $350 tops (I still had a 9" Pengo & a 12" Pengo along with the cheap 6", so was looking at the PHD only). As it turns out I paid $1700 for a hydraulic PHD, sold my 12" Pengo to a friend who was borrowing it for what I paid for it. Got another 12" Pengo with a 2" hex drive to fit the hydraulic PHD. All the 3pt PHDs use a 2" round connection.
I wouldn't pay more than $500 for a Speeco + 2 augers in good used shape. It wouldn't be a good commercial solution, but would do good for somebody on under 30 acres or so.