As for economy, I'd have thought there's a fairly reasonable thought that if you can afford a £10k stereo, you can afford a bit more electricity. It's an argument for the tight-fisted
If, however, you want them to save the environment, then I must admit that I think you're completely deluding yourself. Firstly, I would advse anyone to search on the net for 'global warming lies' or the like, to therefore read both sides of the argument, and to make up their own minds about it. Even if you do believe in man-made global warming, there's far better ways to trim CO2 emissions than to save 40W on a lightbulb.
Did you know that to produce 1 tonne of aluminium (the B&O material of choice) it takes half a tonne of carbon anode plus around 10 tonnes of CO2 generated electricity, plus quite a few more to fabricate a component and ship it? If you take the price of $30 per tonne of CO2, as the next set of emissions certificates are likely to cost in the EU, then you're probably far better off never buying B&O ever again than switching to energy saving lighbulbs.
Plus they look terrible
Plus I actually work for a mining & metals consultancy, I know what I'm talking about