There are TONS of USB drives out there. Many at substantial discounts. However, a great number of them are cheap because their performance is quite terrible. Some read well, but write terribly slow. This can make a good deal on a USB drive a bad deal when it takes 10 minutes to copy to/from it.
Here’s a great website that will help you. It lists hundreds of the most common USB flash drives and ranked by overall speed, read speed, write speed, and price.