The expectations for the BD and the DVD weren't going to be the same, not to mention there wasn't a precedent for how well a series like this was going to sell, nobody knew - it could have been the most profitable thing MangaUK have done in a long time. The pricing is an awkward point because of the exchange rate - just to produce the discs would be at a higher price point than America, then coupling in the fact that the UK is a smaller country: it's a necessary evil, and one that might have even gone down if people went out in their hundreds to buy it.
(But again, I really don't care! Where's Paradox?)