One of the services my business used to offer was refinishing and polishing marble (and other stone) floors. I like to use this project as an example for these kinds of discussions because it is a very time consuming job but the skill sets of people working it vary drastically.

You need to have one primary person that is running a rotary machine with a diamond embedded pad on it essentially scratching the surface of the tile. This person will also be the one later polishing the tiles with a paste. This person needs to know what the hell they are doing. You also need one more person who has a good idea of what they are doing because they will be the one to clean up the tiles after it has been scuffed up and they will ensure the excess paste is cleaned off after polishing process as well. They need to have a idea of what the tiles should look like before and after polishing. Then you have one or two more guys doing the grunt work. Getting clean water, moving equipment and tools, scraping gum and other gunk off the floor before the machine gets to it.

All parties might work 20 hours on a project but we would typically pay the main guy 35 an hour, the second guy 25 an hour and the ones doing the grunt work 17-20 depending how experienced they were, how long they had been working with us and if they did other types of projects with us etc.