Buying used, US to Canada, tax and duty?

Can someone please "clarify" outrageous UPS bokerage fees in dollars?

I've heard fees ranging from 18.00 for a grandmothers care package to 250.00 for audio stuff or automotive aftermarket motor parts/body kits. So I think it really does depend on the product/function and origin of manufacture..p.s. in one week I have never read so many negative experiences with UPS..my preamp is arriving USPS..

Chryslers_rule, my pre amp arrived intact, no brokerage fee, no 'duty' but I did get railed with BOTH gst and pst?? 103.00 plus the usual 5.00 handling bit..

I suppose they would charge duty + GST but on what amount?
The duty guys can't tell the value of the parcell unless there's a sales slip on it can he?

If the sellers says he sold it for 5.00$ plus shipoping, how could you get charged on a higher amount?

USPS as in Us postal services? I'm asking 'cause i'm about to buy a preamp across the border. Is that the way to go to avoid beeing ripped off?

Thanks