Lots of people are recommending Silencershop here. Did you know there is another company that Silencershop is replicating in terms of business model? Starts with an A, ends with a N and trades with a ticker symbol AMZN. No points for guessing it right though.
As an FFL and SOT or as a buyer, the barrier to entry in Silencershop(SS) is really really low. But if you look at the way SS operates, they make SOTs completely dependent on them, takes away almost all earnings and explicitly fucks with brands that they don't carry. They make the process of selling suppressors outside of SS very very very difficult. They actively price fix using their purchase strength. Manufacturers lose on profit, dealers are squeezed dry and consumers do not get the service they deserve. There are very few manufacturers that has told SS to fly kite for trying to squeeze prices. One of them is ThunderBeast and I actively work with them. If you go to a dealer after a sale with questions, the only reason they might help you because SS forces them with their predatory contracts. So the support you generally get is only up to the extent of "fulfilling the contract". As SS completely insulates the dealer from the manufacturer, no relationships are formed. I, for example can pull some strings with manufacturers in exigent circumstances but good luck with that with SS. And that single shot trust they offer is a hot pile of garbage. I have heard many many SOTs with Kiosks say that they are going to stop renewing their SOT because they earn 2, not even 3 figures from an almost 4 figure silencer sale.
I have looked at Silencershop as a FFL/SOT and decided I am better off on my own. I did have to invest in a fingerprint scanner and understand quite a bit about the eForms process. I also set up relationships with National gun trust and a traveling notary. I also set up a corner for taking photographs. Considering I am a software engineer, it was a no brainer for me both financially and technologically, but I understand that it could be hard for independent dealers who does it for a living. You can literally walk into my place with a witness, a driver's license and a dollar note and leave with a control number for buying a suppressor through a trust in 30-45 minutes and I get to keep a little profit and a lot of motivation to help you with after sales. As a customer, you get a promise that I will take care of you with no additional financial commitments in case of any troubles (barring intentional destruction). I even handle the shipping.
Long story short, think before what you wish, because look at what AMZN did to everyone including buyers.
Disclaimer: In case you have missed the idea, I am a FFL/SOT that tells SS to go pound sand.