"oh, that's common practice"

When you buy a house you generally put up some "earnest money" so that
the seller takes the house off the market while you arrange a
prepurchase inspection. You can walk away from the deal after the
inspection, but you forfiet the money. Or you can go forward with the
deal, but negotiate who's going to pay for fixing what. You can use
the inspection as leverage to lower the sale price. That's common
practice - in real estate.

Never came across it in buying used motor vehicles, though.