Maximum transfer rate of USB mass storage device using micro-controller
I have just implemented a FS usb connection on a STM32F3 (72Mhz). I dont' know for the HS rate, but about the number of cycle used by USB, I would say not so much.

I used an FSK algorithm which processed data all the time  and take something like 75% of the CPU cycles, but the USB connection (VCP 115kbps) was ok and not disturb the algorithm, whithout DMA.

If you have the answer for the rate at HS speed, please post, it could interest me!

Seb.