You should find more 430's for sale than 400's, nearly double the ampont of 430 to 400 are registered, interestingly though, sorn records for the 430 to 400 are 5 times higher for the 400.
Are those sorn ones the kind we see in the corners of dealers who can't shift them, i know of 2 dealers local to me who have 400's and to be honest they have seen better days and they not asking much either, may get one for the running gear alone.
Some people do buy big luxury cars and not just Lexus and they don't realise the costs of keepning them in good condition when any kind of issue or service comes up, this then lets the car go unloved and slowly starts the road to the scrapper.
Another reason for sales could be due to running costs, admittedly fuel is lower at the moment which we all can benefit from, but i'm thinking of parting ship for better economy.