That's exactly what i suspected. 40 from 85,1 will be 47% and it is clearly less than 50% don't you think so? Also, i doubt that seller has put $85,1 price on his model, you probably gave here price with applied discount, right? Price offers are always based on original price, because discounts are not applied in that case, so your percentage in fact might be even lower. Try to approach with more reasonable offer, as most buyers won't even consider 50% offer.