I think its up to the individual to do the research and make a decision, if you haven't done the research regarding mpg/running costs etc I have little sympathy. Obviously if your circumstances have changed and your budget has then fair enough that's unforeseen.
I've had my 2006 RX for just over 2 months now and while I've had to become acclimatised to filling up a lot more having come from a 46mpg Honda Civic, you just can't compare the two vehicles. Theres more to driving and ownership than just mpg - comfort, luxury, features, solidity, lifestyle, flexibility, prestige, all these things count to me and while yes I've worked out I'll be paying several hundreds pounds more a year in petrol, I'm hoping that the legendary lexus running costs will offset that. Personally my wife and I and my daughter really like the Lexus for all the reasons I've outlined.
Its a lot of car for the money and I'm avg 33mpg :) Easily do 37 on a 50/60mph run which considering the performance and size is astonishingly good.