I run my own shop and continually struggle with installer compensation. A good installer can be worth up to $30/hr. The problem is that egos being what they are, I have yet to meet an installer that didn't think he was God's gift to electronics. I have therefore separated installers into three levels.

level 1: basic wire monkey. Knows how to drill holes. knows difference between wire types. can read schematics and test wire. ($10-$15/hr)

level 2: level 1 + knows how to connect and calibrate equipment, set up IR systems, assemble equipment racks.
($15-$20/hr)

level 3: intimately knows all equipment including computers, projectors, etc. Can perform ISF calibration and program Crestron and other remotes. Also has the ability to perform advanced trouble shooting such as power line noise and ground loop problems. (>$20/hr)

The main thing is that each level needs to be able to test and document their phase. They DO NOT get paid to fix their own mistakes. If something happens to the installation in the construction process I need to be able to back charge to fix it or I won't be able to pay the installer.

Lastly, I pay a 5% commision on the total amount of the upgrade. Of course I then have to have a talk with salesperson about why the upgrade wasn't sold at the initial presentation.