The point really isn't "what they're selling for" as the simple truth is, you're right, on the EE they aren't coming up often at all.
The point was that you made it sound like the world would end if he decided to go anywhere else and buy it.
The truth is, I have no doubt if you spent a little time on ebay or on American forums, you could very easily find the parts you wanted at a reasonable price. Yes you'd have to ship them in, but no they won't get held up at the border because they're related to guns, and no they won't charge you a huge duty/tax when you bring them in. FAR more often than not, I never get charged duty or taxes on anything that's valued at less than a couple hundred dollars. In fact, when I use USPS, I dont' think I've been charged duty more than once on any item worth less than about 3-400 dollars.
So my point wasn't that you can go down to wholesale sports and buy the same thing you're selling for half the price. The point was that the world will not fall apart if the OP goes on ebay or a US forum and finds the parts he wants, and he'll be able to find them at a decent price if he's willing to put in some leg work to find them.
You're selling your stuff, you have every right to ask whatever price you want. That's fine. But please don't try to use fear of duty or delays or not being able to find it anywhere as a justification for a super high price. Just say it how it is: "My stuff is priced really high because it's available, in Canada, and is uncommon here. If you are willing to spend the money to get something quickly and easily without looking around, I'm your guy". That's the honest truth - if someone wants to save the effort of searching, then I'm sure they might be willing to buy it from you.
