In my experience, restores run at about 10-15% of backup rates, so you are right in the ball park
I've never had anyone give me a reason for the difference, but it seems to hold across multiple versions and tape drives (for me at least) I assume that it has something to do with having to create the MFT entry before actually writing the data to disk, and the associated overhead of random access writes, while the backup is straight sequential writes, but that is strictly conjecture on my part