The collection actually never came out in North America. So that's why you see some people asking crazy amounts since this is an import and they automatically think that means it should be expensive.
Being exclusive is also why it's likely region free, allowing them to capture some import sales that otherwise wouldn't of happened. All of the region free 360 releases from UK that I'm aware of have one trait in common. They either were never released in North America in any form (WRC II, for instance) or were digital Xbox Live Arcade exclusives over here like this collection or the similar Ubisoft one that included Beyond Good & Evil HD.
Normally, it's probably not a risk worth taking on the Xbox 360 in the West to save a few dollars since region locking predominated. Without knowing with certainty that a particular release is region free, you'll likely end up disappointed in the end.
Let me know what you think about my reviews.