The $12k battery placement cost is not included in the spreadsheet, not to mention that this is the cost if purchased 8 years ahead of time and purchasing it later will probably be more expensive.
He's already bought the car and so he should know how his insurance cost has changed, but doesn't mention how much it changed.
The model also does not include property tax. I'm assuming California has a car property tax of some kind.
...so basically this is justifying his purchase to himself, little more than that.
I think making a domain entirely dedicated to it is evidence that it wasn't intended as just self justification.
edit: On further thought, maybe not. It does seem to be the trend to do websites for a single topic or piece of writing. I would still take it as indication you are presenting it to others though.
As long as he indicates that it's anecdotal (as he did throughout the piece) I don't see an issue with sharing it with the world. It's not like he's selling himself as a car buying consultant; he's just sharing the fruits of his private labors with anyone who it may help. He's a Harvard MBA grad; I'm sure he's proud of his skills. I can see that fostering the desire to make a dedicated website. But then, I tend to see the best in people before considering the worst (which is probably why I'm not a businessman at heart).
He's already bought the car and so he should know how his insurance cost has changed, but doesn't mention how much it changed.
The model also does not include property tax. I'm assuming California has a car property tax of some kind.
...so basically this is justifying his purchase to himself, little more than that.