Standard pricing? An hourly shop rate at around $75 with a 1/2-hour minimum and turnaround time of a few days. If you need it right away you'll usually pay a premium rate to jump to the front of the line.
A little bit of unsolicited advice follows
Your first problem is doing it on your own time. It's all fine and dandy to be "the nice guy" and jump in when needed, but doing it for nothing isn't fair to you. I see that you work for a small company and I'm guessing that you're probably pretty happy there if you go to these lengths to make sure things fly right - kudos to ya.
If you really want to make an impression - write a short report/memo about what you think went wrong. Address the fact that they had no backup and that it was your abilities that recovered the data. Put a little bit of fear into them - "How important is the data and what happens if it's gone for good?". Also mention how much it would cost to have the data recovered in the same timely manner which you did it. At the very least you should be paid your wage to do the recovery