consider this, since you are the expert in auto v manuals!
Its quite probable that Tranny fluid will never be changed in the ownership of a car, should someone have the misfortune to own a is250 manual (tongue firmly in cheek).
As for clutch failures, show me some posts where clutches were bust on a Lexus? They should last the life of the car, assuming people can drive propely. Auto and Manual is250 cars have pretty much identical running costs, contrary to your expert opinion
That brings us to tax, its a bit expensive by a few hundred quid, but expensive enough to put people off them and buying cars on lower VED bands.
People worry about car tax, no iffs and no buts. Its one of the reasons why there has been a deluge in people buying diesels over the last decade or so.