At 10 years, you are likely at the very brink of the lifespan of the battery pack.
The 60khw battery pack (since we're debating the bottom end options here) gets ~200 miles per charge. I would anticipate that would drop off over the 10 year life span we're looking at, but I don't have hard numbers on it.
1 kwh in Wisconsin costs ~13.1 cents. So roughly $7.86 full per charge (~4c per mile).
Comparatively, I'm spending ~10c per mile on fuel for my Golf TDI.
Figure ~13,000 miles driven per year by your average American. $520 for the Tesla, $1300 for the Golf. So you come out ahead, on average, $780 a year. Over 10 years, the savings on fuel is roughly half of the $15,000 you mentioned, assuming it can maintain a 200 mile charge for the 10 year lifespan.
But, you also have to look at the costs of the loan. A $70,000 car note over 5 years is going to cost ~$10,200 in interest. Compared to a $22k car (VW Golf TDI) where that same 5 year note is going to cost ~$3,200.
So the fuel savings ($7800) is almost entirely wiped out by the additional interest cost ($7000).
There are other savings, probably a hundred dollars a year in oil changes, the 100,000 mile timing belt ($800), but most of the other maintenance matches between the two cars.
There is really nothing here that makes it easier to swallow. If you want a $70k automobile as an upper-middle income household of 4, you will need to make radical spending changes and/or live paycheck to paycheck on the edge of your finances.
Wait for the kids to go off to college and buy one for your mid-life crisis.
-Rick