If you are not on BP, the maximum discount you can receive is 20% regardless of the size of your order. The only difference will be the freight charge, if your order is under 75pv freight will be $9.95 and 75PV or higher it will reduce to $4.95.
If you are on BP, the maximum amount of freight you will pay is $4.95 for orders under 75PV. All orders 75PV or higher receive free freight. You can also receive higher discounts than 20%. Orders of 130PV up to 699PV receive a 30% discount and 700PV and above receive a 40% discount.