narf
Sgt. Maj. Buzzkill
Some of them even care about environment.
And the tax % is much lower for the diesel.
Ignore the taxes for now... the 650i simply consumes 70% more fuel than the 635d. Even if diesel is a bit more expensive as it apparently is in the US, you're still going to save shitloads of cash.
Also, the 650i has a range of under 600km on a full tank. A 635i will take you over 1000km between fillups. As a driver who worked itself towards the riches, that time saved is worth a lot of money. If you inherited it all and are looking for a way to get through the day then yes, spending more time at the pump sounds like a great idea.