I agree. Suppressors are basically a miniature car muffler. Granted, they are machined to fit a particular weapon and precision crafted, but they are not worth the outrageous prices of today.
One of the most popular weapons is the AR15, one would think mass producing a silencer for that weapon would bring the price down to less than a hundred bucks. They could be accessory items on the shelves of all sporting goods stores.
There are already dozens of companies that make supressors for the AR platform. From .22LR up to .300BO.
Pretty much every caliber, up to and including the 20mm, have at least 1 manufacturer currently kicking out cans for it. Some cans are even multi-caliber.