How are data recovery charged? Is it per hour and if so how much?

I feel someone is being irresponsible. This guy came to repair a machine in our office that wouldnt boot. The first thing he tried was reinstalling win 7. 

I would expect that to be the last option. So when the installation failed, he took the laptop to his office for data recovery

A day later he comes back with a bill of Kes 4,500 per hour for 16 hrs. (Plus screenshots)

Unfortunately I was away while this was happening as I feel I could have handled it better. As far as I can tell, the hdd was readable therefore it was completely irresponsible to attempt a reinstall without backing up data and then come back to charge us for recovery

If the guy(s) involved are skunk members they are giving us a bad name.