United Kingdom-based electronics retailer Clove, and at present it's set to ship sometime in April. The phone is going for £399 unlocked (about $636 USD) and £478.80 after value-added taxes.
Clove likes their gadgets too, but apparently they've got some inside information: they say the LG Optimus 4X HD will hit their shelves in an unlocked version by June. The price is currently listed at £380 before value-added tax. That's just over $600 US, and fairly typical for a UK superphone. All this is subject to change - Clove and other retailers have a history of guessing at release dates, which are prone to unexpected delays in any case. Unfortunately, they also say that the new LG Optimus 3D Max isn't coming along for the ride.
on their official blog. [ed. note: blog appears to be down at the moment]