Well, it is roughly £350 over 10,000 miles assuming it is 10mpg. I suppose it depends on what figures actual IS250 owners are getting mpg wise. According to Lexus, the IS250 is doing 31mpg combined whereas the IS220d is doing almost 45. With those figures, the cost would be nearer £530.
Also, admittedly not the largest concern, but the road tax is also £85 more expensive. Not a great deal in itself.
Finally, the 250 is one insurance group higher than the diesel.
I admit none of these are huge concerned in themselves, but it all adds up in the end.
I agree though, that if it wasn't for the cost, the IS250 Auto is a much more accomplished Lexus