Owner of both a Tesla Model 3 & a 2021 Sienna here. Just want to double check your math. Seattle, WA to Detroit, MI is 2367 miles.So traveling in Model Y which in theory can accommodate 7 people (yeah right, more like 4 adults and 2 kids) it'll cost about $3.1 per 36 miles traveled ($0.28c/kWh) - charging at superchargers. While Sienna 2021 can do 36 miles on highway (in theory if driven at 70mph) for 1 gal of regular fuel - which costs on average about $2.9 currently across USA.
- Model Y with 1500lbs of cargo would cost you around $120: A Better Routeplanner
- 2021 Sienna assuming 33mpg highway when loaded with 7 people and $2.90/gal would cost $208
The charge vs fuel time would be the killer. 21 stops totalling 5h 41m of charging for the Tesla vs 5 stops totaling 1h 15m for the Toyota. Now the Tesla would cut out 3 of those stops assuming you did the drive in 4 days and you'd save a few $ on the Tesla assuming you did an overnight charge at your hotel which is generally free.
I'm not going to argue that the Sienna is not a better road trip vehicle, hence why we have one AND a Tesla for all our around town driving. That said, even at supercharger prices gas has to be under $1.82 / gallon and the Sienna would actually need to get 36mpg fully loaded with people to be less expensive per mile than a Tesla using Superchargers.