I am sure the a smart japanese seller will also know fullwell that they'd never get the price for a local buyer, but there are plenty who will pay the extra price overseas.
So many would set a high reserve I'd imagine, just hoping silly westerner buys there car for much more than they would be able to sell it locally.. even though to the westerner they are getting a "good" price (and they might be compared to local prices here).
Then they just rub their hands together as the car gets driven away and onto a boat and they never have to worry about it again.. hell if i could sell my "fullsik" r31 which i bought for $1500 locally, for $4000 with the potential to sell it "as is" to somebody overseas in china or something.. who thought they were great cars.. I know i'd be doing it.