Good ones wouldn't.
The reason they cost what they do is because they're built to be lifetime investments. The materials, manufacturing processes & tolerances are orders of magnitude above inexpensive things people like to compare them to. Car mufflers, even good ones that sell for north of $200 each, are made with cheap sheet metal, are much simpler inside, only have to contain a few PSI, no heat treatment, little concern over finish durability, and have tolerances in fractional inch.
There are already some very cheap options; people don't buy them because they're garbage. I'm sure a lot more of those would sell without NFA, but I don't think it would put a dent in quality suppressor sales, because the people buying them in droves would be the people not buying anything presently.