There was a post on here last week with this at £20 on Amazon, and at the time it was also £20 in Tesco.
Been into the Copdock, Ipswich branch this morning and they had about half a dozen on the top shelf where the toys are marked at the ridiculously low price of £7.50!!!
I also got a die cast transformer (blackout) which on the shelf edge was marked down from £3.99 to £1.99 but went through the till at 49p!
Obviously not all stores will have these, and I haven't checked online, but if you live near a big store and want one of these, it's probably worth a look!