cellio | Amazon price wackiness

I don't really understand Amazon UK right now, but I guess I'm glad they're looking out for my finances, whatever they're doing.

Last May I ordered a DVD for GBP 31.90. Over the course of the next nine months the price rose (and the release date changed numerous times). Whatever -- I had a price commitment, and if the price actually dropped I could always cancel the unfilled order and try again. Hard to lose (price-wise) under those circumstances. Financially, I was completely satisfied.

The DVD recently arrived. I paid GBP 31.90. And then I got email saying that (1) they've reduced the price and (2) I'm entitled to a refund of GBP 5.94 (or maybe half of that; I can't tell if this is a number for the order of two identical DVDs or a per-DVD price). So by that reasoning, they think I should have paid GPB 25.96 or GPB 28.93.

But their web site currently lists the price as GPB 33.99. Huh?