What is the average dealer mark up?

What you have to look at is the monthly profit and loss statement. Cost of rent. Federal, state and local taxes. Inventory on hand, Employee expenses, medical and general insurance, electrical bills. Office supplies even mundane expenses like trash disposal. Lot's of costs involved in running a business. That percent isn't 100% profit that you put in your pocket.

Here is an example of a quarterly P&L 
Revenue: $170,946
Cost of Goods Sold(COGS)$88,244
Gross Margin:$88702
Gross percent: 52%
Operating Expense $21,946
Operating Income:$67,106
Taxes: $9927
Depreciation: $1025
Total Expenses: $114,692
Net Profit: $56,254
Profit percent: 33%
This is a synopsis of a company that I worked for many years ago. A short example of where the profit goes. Unfortunately most people never look at a companies P&L statement and only look at the Revenue at the top.