First, the promoter/track sets the pit pass prices. Second, most sanctioning bodies USAC, Woo, All Stars as part of their sanctioning agreement have a clause where their members get a discounted pit pass (usually $5-10 cheaper) or free pit passes to so many members per car.

To my knowledge USAC is the only sanctioning body that subtracts a $100 from non members feature purse. Now Woo mandates you must be a member to even race with them so you have to pay a $150 membership fee to even pull your first pill draw. Other local tracks or smaller sanctioning bodies have a $20 or $30 entry fee at pill draw.