UPS has a schedule of brokerage fees. It is on their web page somewhere, but they do a good job of hiding it.

It's something like this:

$0-$100 = $X brokerage fee
100-250 = Y fee
250-500 = Z and so on.

Percentage wise, it is worst at lower cost. I will never voluntarily use thier shipping service, it is a rip off.