The reason you only see 10MB/sec is that those performance counters look at data from one second to the next, rather than singular actions within the same timeframe. So your query may have pulled 10MB in less than a second, but that'll only register in Performance Monitor as 10MB/sec.
A backup pulls large amounts of data across the board, so it'll register at the disk's full speed. Were it able to register disk IOs for individual actions, it would probably say 200mb/sec or something similar, possibly even more for smaller packets of data since speed becomes almost impossible to gauge for small packets.
Hope this helps.