It has more to do with lack of competition that difficulty in manufacturing. In many other countries, where they're not only legal but sometimesrequired, silencers can be had for $50.
Another factor, I think, it that the approval process is expensive and time consuming so we (the American consumer) expect to get a very high-end product for all the time and money.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.