There's a difference between dumping individual cards on eBay (that's fine because a buyer knows what they are getting), selling stuff that you know is unlikely to have the advertised ratios or worse, selling sealed box case remnants after securing the case hit(s) (searched case remnants). The latter is the main reason there are very few sellers I would buy a loose sealed box from. There is no way in h*ll I would but a loose pack off eBay!
I totally agree with Matt though, there should not be "newsagent stock" to have to worry about. Either increase the number of rubies (and case cards) or reduce the number of cases so that the rations on the packs are actually correct (or at least 99% correct).