As a matter of auto industry standard...dealer cost and sticker price "usually" vary by not more than 5-10% of the list price. That's $1500 to $3000 on a $30,000 car...not very much considering the expenses.
There's virtually no money made on selling cars. I bet it barely covers the sales commission and dealerships utilities - let alone the mortgage and interest costs, taxes, franchaise expenses, and the salaries of support staff.
The money's made in parts and service.
Good dealers do well. Poor dealers end up selling or bankrupt. I still remember the old days when Chrysler dealers we're going belly up faster than an XRS at lift.