I picked up a air cleaner foam element for my CT90 yesterday at the local bike shop. Needed in a hurry because I found the old one had disintegrated and I'm trying to get it on the road ASAP. Cost me $29. On the US parts sites they are about $8.50 and the $A and $US are pretty much on par now. 
The prices aren't affected by any import tarriffs. I just assume it because of competition in the North American market. Our dollar has gained about 40% strength in the last 2 years and nothing has got cheaper.
I drove a jeep 26000 miles around North America in 1995 (25 US states, 3 Canadian Provinces) and did a fair bit of maintenance along the way and just couldn't believe how cheap everything was and that was when our $ was only worth about US74 cents. I recall before I sold it I had to replace front brake pads and rear shoes. Total cost was $32 and that included free machining of discs and drums at the auto parts store in Washington DC.