(128 x 450) + 11900 = 69.500 e-cash
(128 x 250) + 6900 = 38.900 charged RPs

That means almost 400 $ charged RPs without fail, its crazy
And you are wrong if u think that u will fail once or twice, fail at +3 is relatively cheap, but count how much is every fail at +5 / +6 / +7
I would say that rate at +7 is around 15%