lower price comes with lower quality parts, or lower attention to details

I disagree.
A shop in rural Arkansas has far lower overhead costs (income tax, permits, waste disposal, water, property tax) than in Manhattan, the prevailing wage for low-tech shop labor is lower, and the amount the owner needs to keep himself in groceries is less.

If the prices were the same, the Arkansas guy is getting rich and the NYC guy is bankrupt.

Eventually, some bright person is going to realize that Mexico has no OSHA, no building regulation of any kind, no unions, labor is $3.00 an hour for grunt work and $20. for machinists, and the highest overhead is the Chief of Police gets $100 a week to ignore you.
If you're careful, there won't be any import/export duties or problems either.
Mexico doesn't care what "used car parts" you bring in, and U.S. made goods returning to the U.S. are exempt.