Amazon shops have now opened up for pre-order of Might and Magic: Heroes VI

Amazon.com sets the price at $50, with a release date of May 10th. The offer contains a price guarantee which says that "if the Amazon.com price decreases between your order time and the end of the day of the release date, you'll receive the lowest price". They don't specify if this guarantee is extended if the release date is changed.
Amazon.co.uk has a different release date (May 27th), and sets the price at £30 - also with the pre-order price guarantee.