Ones from the UK (HMV exclusives) seem to run about $38 or thereabouts shipped.
With the German one, the same thing happened with Tron 3D - it was something like $46 before shipping to folks in the US (so maybe $50 total) and then it dropped down to below $30 or around there later on.
With Paramount steelbooks, the actual steelbook is GOING to be the same, we've seen it enough lately to be confident in it - so really you're just paying more for the content.
In my opinion, you can always get the 3D disc later, so I prefer to get the cheapest version of the steelbook.
I've heard lots of good stories of JSDVD from folks on this forum, I have never ordered there myself.
Finally - it also depends on the release, if you're doing your order, it makes sense to order from amazon.co.uk or hmv.com or things like that, but for German single releases, you are always going to make it out cheaper if you go with the group buy the organizer is able to get the 14 euro flat shipping.