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I think your experience is the exception rather than the rule. I paid less than $700.00 for my Sanford MG. It didn't need any repairs, or even a cleanup. It came with a chuck, a wheel hub, and half a dozen assorted wheels. I think the key to determining the condition of a machine is to be able to run it as part of the inspection process. Many of the defects you found after getting it home would have been revealed had you been able to run it before purchasing it.
Here's a couple pictures of the machine as it looked when installed in the shop. The previous owner had it clean, wired in, and ready for inspection