How to pay your salesmen?

Does anyone tie there % of sale commission to the current price of material?

So the going rate according to this thread is 7-10% of sale. What if shingles almost double in price again like they did in 2008?

We are not storm chasers. Used to pay 8%. Now according to the math I should offer 6%. I provide truck, gas, 401k, and approx. 25 leads per week during the busy season. A 30%/70% split for anything sold over our base prices (30% to salesman). 10% for door knocks (if they want to). 1 million a year is easy, 1.5 million should be sold, and sky's the limit after that. But I'm looking to attach the 6% to the current price of shingles. Does this seem fair?

Suppose, in Example Z, that a piece of work sold for $11.528.23 but that another piece of work was significantly different? As far as I know, there were no other jobs like this one that sold for as much money octodle. Even though they advertised for entirely different roles, are both of the salesmen at this job fair entitled to 10% of the commission on the tickets they sell?