A reader has just sent in this image from a Currys/PC World in the U.K. where the tablet is up on display at £499.99 for 16GB of storage and Wifi connectivity. Interestingly the processor is listed as "quad core," even though the model hitting the U.S. is an octa-core (but we wouldn't be surprised if this was a typo in the end).
The tipster indicates that the store will actually sell you one starting next week, even though they're already on display this weekend. I don't have any other solid indication of pricing or availability at other stores, although some online retailers such as Clove have the tablet listed at £479.99 for the Wifi model.