As an 07/02 FFL I've got to say that some of the high cost is dealers marking suppressors up quite a bit. I talked to one customer recently who had purchased a suppressor from another local dealer for 20% more than my price on the same can, and we're still making about 15% at our price. So part of it is finding a good dealer that's not excessively elevating the costs just to increase their margin of profit. I understand that it can be difficult to make a lot of money in the firearms business, but we've managed to build a slow but steady and profitable business by treating people fairly and earning a lot of repeat business.
Find a good honest local dealer and you'll find the costs are perhaps a little more affordable than you might be seeing elsewhere.