25 RP card not werf?!

I just finished my exams, so of course I immediately headed to the nearest EB Games to buy RP for my Snowdown splurge. I normally buy the $10 card, which gives 1350 RP. However, since it's Snowdown and all, I decided I'd get the $25 card. If the cards were increasing in worth uniformly, the $25 card should have been 1350*2.5 = 3375 RP. But I only got 3250 RP. It's worth less in RP than it should be. This should change...