Customs and Duties for non US Sales

Wonder if anyone knows the answer to why this happens. I have purchased things from Canada, Hong Kong, and the UK. The time I bought from Canada the seller used UPS. The sellers in HK and the UK used the equivelent of the US Postal Service, and then I received the package via USPS. In the non UPS transactions, I never incurred customs and brokers fees. I called Fedex and they stated that in all shipments from out of the country, no matter what the product is, they use a broker(fees charged to me) Anyone know why then, UK HK and USPS so far does not need the same type of brokers?
Here in Canada when using UPS for inbound items they will add in approx. $40 (cdn) for brokerage fees which they do not tell you in the quoted rate for shipment. I believe that FedEx covers these charges in the quoted rate and hence are more expensive. I have had some success when using USPS for incoming items. The biggest issue is to claim that it is used audio goods and the country of manufacture. When its the USA there is supposed to be no duties (NAFTA) but we do get taxed Provincial and Federal (where applicable) plus the Canadian Post office gets $5 for collecting & forwarding your money. I think that the Postal service is the best route as you can purchase insurance, track your packages and avoid the fees. It just typically takes a little longer...
I'm in Canada and have purchased numerous items from the U.S.A. In general, I find that USPS takes longer, but there's only the $5.00 Canada Post handling charge plus sales tax. UPS adds, as Rdg mentions, their rather stiff brokerage fee, plus the sales tax, plus at least half of my UPS packages arrived with some kind of damage and in no case was UPS willing to honour the insurance claim. So far I've had nothing damaged using the postal service. Within Canada I use the post office or, for heavy items like speakers, Grayhound bus. Again, no problems there. Hope this helps someone. . .Happy listening all. Joel Tatelman