Depends entirely on your location and who you are dealing with. In my area I have not seen AFB in ten years. But previous to that I bought a pile of dead outs from an elderly beek who swore he had no AFB and I used that equipment to start thirty nucs and everyone of them was full of AFB. I had to dispose of all the frames and scorch the inside of the boxes and that was that. So since you can scorch covers, bottom boards and boxes that sets a base value for used equipment. If Joe and Jill Wannabee got their new hives, put bees in them and never looked in them again, they swarmed and failed to requeen and died out, that discouragement sale is a bargain because the drawn comb is of great value to a new package or nuc and gives them a real head start.
Some states have pressure chambers to sterilize used equipment also and that is worth looking into. Like all things in life and bee keeping mileage may vary. Some bees seem to fight off AFB infection. I would not knowingly buy used equipment or buy nucs from anyone who I know to regularly feed terrymiacin extender patties spring and fall so they just never have a problem. They are breeding resistent AFB! Also looking at pictures of the disease and more important smelling it, will go a long way toward not buying infected equipment. Never pay more than new! But bargains from disallusioned new beekeepers are normally a bargain.