I would like to get some more info on how the coupon was enabled, quick understanding of the tiers makes me presume that it was a higher tier with most tier requiring multiple months before receiving the rewards, thus meaning that the cost must be further reducted from the coupon granted, if we take 3 months as the min on highest tier that would mean a reduction of 150 from the coupon meaning the cost was 350 (I don't like when people try to exaggerate their pains).

Furthermore you are telling me that using one coupon for an item is nigger behavior if the seller makes a mistake in their cost/ratio? I could potentially see it if you are setting it into systemic use, but if I see an item I want and i got a coupon why would it be my duty to ensure that the entire production chain is valid? That is a insane system of bureaucracy. I hope you know every step of purchase you do and their full production chain, I need to know every margin is correct?

Do explain how it is the customers fault in this regard.