First question: Steelbooks always command a premium over amarays, especially Disney Steelbooks. Second question: a company can't be competitive all of the time and Universal are known for their high prices anyway (often around £20). No doubt it will be £9.99 in a few months anyway.
I know it's the in thing to diss Zavvi, but I think a lot of it is uncalled for. The Germans have been pumping out Steelbooks usually of a much lower quality for similar prices for years, yet Zavvi get a bad reputation. I don't see Amazon.de getting as much criticism despite them charging even more than Zavvi (or Entertainment Store for that matter). Yes you get comments about the price but you don't see people saying that they are ruining collecting or making YouTube videos on the subject.
EDIT: I forgot to say, it is not Zavvi who are ruining this hobby, it is the collectors who constantly ***** and moan about everything. If it's not the film itself; it's the artwork, embossing (or lack of), the paint finish, the lack of content, the print run, the price, the release date, the retailer etc.