it looks like you are getting your kb (kilobits) mixed up with your KB (kilobytes).
70-85KB/s is correct and you are getting your full upload speed (minus a little for overheads).
http://www.matisse.net/bitcalc/ this is a calculator that will convert bits to bytes but basically tou just have to divide the bits by 8 to get the bytes.
virgin upload=768kb=96KB
Edit:- LOL, got beaten to it.