On Sale Champion Cost Me Full Price

When I saw Vel'Koz was on sale, I really wanted to buy him, so i did. But when i bought him, my RP went down further then i expected. So I added up all the RP I had expended since my last total which was about 2,856. And I when I added it all up my total was 2,368. Obviously the difference of 975 and 487 is 488. And 488 + 2,368 = 2,856 which was my previous total. This pisses me off that the on sale champion cost me full price when it was obviously on sale for 488 less. Refund or something please. I was lucky that I even noticed the math was weird, or else i would've never seen it and played on.