Zavvi and HMV DO pay the same price for releases. That being said there are certain titles and studios that demand a higher £. Disney basically price fix and always have done, and certain power players within Hollywood expect distributors to ask for more on their titles "Mr Cruise" being one.
Zavvi 99.9% of the time are always more expensive and harder to sort a price drop with than Amazon who normally by release day match or lower. Zavvi play the game of home of steelsbooks, and try to sell out as fast as possible by using marketing that often works well, although we know its bogus now most of the time, but it works, Amazon are so big they don't care about that, their much better customers service, "usually better packaging" means often they sell out just as fast.
We've watched Zavvi sell out average titles fast with bad art, just because 1.. Steel nuts have to have them, 2.. They market well, limited edition, low numbers etc. It's worked. Cruise sells and low number = Jack Reacher all over again. My "guess" is this will sell out or at least drop till they have very few left, but then Cruise isn't as big as he used to be and films like the recent Fast titles while earing big money in cinemas ended up in the bargain bin. Stick a Marvel logo and SELL OUT and prices double on secondary markets, everything else these days as
@lgans316 says you can pretty much get on eBay for cost or less within a sort time.