If the japs had ahy sense buying mx bikes they certainly Wouldn't buy them from the uk, they'd buy them from the states, where they're cleaner, cheaper, and closer to home. The reason all mx bike prices are on the up (2&4) are because of the massive amount of bedroom traders that have sprung up buying them, then advertising them in the same place the next week for 25% more, people with half a brain are seeing this and thinking 'why the hell am i letting someone come and make 500 off me for doing nowt, i might aswell advertise it at that price myself?"
In the future, 3 to 5 years in my opinion, a super clean low milage import might be worth 8k, but not now, as you said yourself, they're still readily available to import for 4-5k , when that changes so will the price imo.