I would say there are four factors. One is that kilt jackets are more complex than a standard jacket and second is a numbers game. I would be willing to bet that the average mens clothing house runs more copies of one jacket in any given colour than all the kilt jacket manufacturers run in total. Third as arrogcow said most kilt wearers use them for more formal affairs they want to buy what they feel is quality. Lastly (and this also goes with my second point) I just don't think there is enough total volume to get lower cost manufactureres, who take small mark-ups but move high volume, to get involved. In other words I don't think there will be a Walmart equivalent of kilts any time soon.