It has no bearing on the calculation. You need to compare the tax savings with gross sales to say how much you can reduce prices. But you don't like to do that because it shows how little those savings actually are.
Gross sales have nothing to do with tax savings. Gross sales are only half of the equation. You can have all the sales in the world and have equal expenses and have NO income. You wouldn't have any tax savings and you also wouldn't be in business for very long.
Do you figure your tax liability on your sales or your income?