I imagine when the full game does restock it will likely be around 50 USD + 7.50 for shipping, which again is almost double what you can get the base game alone for on Amazon.co.uk.
How is this almost double? I'm looking on Amazon.co.uk right now, and I see it for 35.08 GBP / 54.08 USD, and that's without shipping. When it was in stock, Keyflower typically had free Prime shipping, to make it an even $50.
EDIT: Just noticed the timestamp of the original post. Whatever price the base game was before might be dead now.