Most states limit the max outlay required before they give someone a pass. In some cases, a vehicle requiring repair expenditures over $450 may get a waiver from the state exempting it from further repairs regardless of test outcome.

You can see a lot of details here. http://www.rff.org/Documents/RFF-DP-99-23-REV.pdf Also, repairs often increase fuel economy so not only do city's become far more livable again the net cost is fairly low.