It is legal to make your own. Form 1 suppressor.
And yeah, damn those manuf. for having employees to pay, advertising, overhead, equipment to pay for, warranties, wanting to run an American business, etc.
Certainly, they have a right to pay their employees and charge whatever they want.
But when I look at the complexity and cost of the pistol compared to a glorified tube for $800-1000 which costs more than the pistol it goes on, it's a rip-off to me.
Then you should start up your own company and produce a superior product for cheaper than they can. You'd corner the market and I'm sure the "Huntertown" effect wouldn't happen
If you can mass produce glorified tubes that can handle full auto flames and pressures, muzzle attachments, pistons, intricate locking systems, and warranty anything that may happen from bad welds on your part to a lapse of judgment on the end users' part then you should go for it