15k each is considerably less than the value of the cover.
1 bundle of 30 costs $3.25 US
All 12 bundles as a set is $12.50 US
The prices in Japan were within about 10-15% of the US costs, IIRC.
Assuming that gold is $1 per million (the less a million is worth, the more gold is worth, and therefore also the covers. IF gold was 67 cents a million, multiply the gold numbers below by 1.5; if 50 cents a million, multiply gold by 2)
If bought as a set, that would be 12.5 million / 360 = 34,722 gold (effectively about 35k per cover)
If bought individually, that would be 3.25 million / 30 = 108k+ each.
If someone is selling them at 15k each, they are effectively selling them at 40% of their cost (maybe as low as 10% of cost) AT BEST.
If I saw them at 15k, I'd buy them even if I didn't need them, JUST TO RESELL at their real market value.