skins cost 2x as much..... watch the vid

so I was shopping with the rp I got as a gift when I realized that when I clicked a skin, where it said "new balance" it showed a incorrect balance, eg, I had 4000 rp and was buying a 500 rp skin the "new balance" part said I would have 3000 left - but that would be only if it was a 1000 rp skin. so, me being the curious guy I am, I bought it. (watch the vid) I had lost 520 rp! they stole it from me!

4575 - 520 = 4055 I should hav 4055 rp left, but I hav 3535 instead! why is that? somebody tell me? please?