Scott is right; the $200 tax stamp pretty much ensures that most suppressors in the US are of heirloom quality... it isn't even just the $200 stamp. If it were ONLY that it would be easier to handle. The real trick is also the extended (5-6 month) wait for approval and the extensive paperwork. If it were only another $200 I would likely have quite a few more (as would others). It's the hassle of the paperwork and the long wait that keeps me from having numerous cans.
Since it's such a chore to get approval for one, you aren't that interested in buying less than the very best. The sting of an extra hundred bucks or two for a quality one is but a memory by the time the Form 4 comes back from Atlanta. A so-so suppressor is an annoyance every time you use it thereafter.
I know if I had to do it again I'd have a different .22 can and maybe a different 5.56 one. When I went for a .45 this time I did my research first and bought what I could determine was one of the very best on the market.