You Do know the UK Price of mojo is £400 and it sells for $550 in the USA? Using google currency thats $495. So its not straightforward conversion mathematics. There are taxes and international retailers own margins involved. So a UK Price of £500 will roughly be around $650 atleast in the US. And I wouldn't be surprised if its 700.
When the Mojo was released the pound was worth $1.60, so the $599 US retail was derived from the then current exchange rate. Due to Brexit, the pound is down to $1.25, so I'm sure the US retail will be $599.