ajw, everyone around me thinks I'm crazy for selling a vehicle thats barely a year old. But I tell them that this is an exception, because it's for a Tesla. My wife will get a kick out of this thread.
To share my similar experience: I had to do a cost breakdown and present it to the wifey using Excel spreadsheets and Power Point slides to convince her that the Model S isn't much more cost than my current vehicle. Of course, I'm exaggerating but it sure seems like that's what I had to do. I took out a 7 year loan @ 1.75% on my current vehicle, so if I'm going to suffer paying another 6 years of payments, it might as well be for a MS.
I also used your rationalization and treat it as a lease. I also got a good OTD price and all I want is for Auto Nation, or whoever, to pay off the loan. Since I am paying a 7 year amortized payment instead of a 5, I figured, my loan balance would still be high so it'd be hard to get the loan paid off. So I look at this way, if I were paying a 5 year loan, Auto Nation's offer would almost hit the mark. But still I could try to minimize the loss, so I'll give Carmax a shot. I'm sure there are flaws in my logic, but whatever, it is what it is and it is for a Tesla. I'm definitely not selling private party, been there done that, flakers, last minute deal breakers, hagglers, etc... not worth my time.
I too am receiving my 4th child at the end of June. I just took a road trip to Reno with my SUV (normally we use my wife's Odyssey) for one last hoorah before we part ways.