So this is likely another test then methinks, along the lines of the Avengers one. With the second Marvel series finishing at the end of last year it makes sense for Hachette to see what brand would do best. Anyways, if it's just a test you can expect the four issues to turn up eventually for free. I've always stayed away from the Marvel collections as I have Marvel Unlimited.
EDIT: Interesting to note there are eight premium books in this collection as apposed to the more common four prints/statues/Oversized BW:Murderer.
Its not a Complete X-Men Collection though and looks to be mainly Uncanny X Men from Issue 94 and X Men Volume 2 with tie in issues from other X-titles. Looks like 60 issues but I'd say it would be at least 80 with an average 7 issues in each volume so around 500 issues ?
I would like to know whats included in the collection I'm guessing most of the big major X-Overs are spread over 2 or 3 volumes.