To help some understand why the Model S could be "cheaper" to own vs a Honda Odyssey it's important to understand a few factors:
1. Low fuel costs - electricity is way cheaper than gas and when you factor in gas savings over 8 years, you get substantial savings (ie., $20k over 8 years if driving 15k miles a year, of course depends on gas prices and electricity prices).
2. Low maintenance costs - there's no oil changes, timing belt, etc. It's basically tires. Even brakes you don't need to change often because of regenerative braking.
3. High residual value due to upgradeability - the battery pack is swappable, so after 8 years (or longer) you can swap out battery packs to a bigger pack (ie., 400+ mile range). This is a great feature and will add residual value to the Model S. Also, over-the-air updates keeps the software always up to date.
4. High residual value due to battery pack - the battery pack for the Model S is holding up well with customers so far, and after 8 years it should show minimal degradation (ie., 10-15% likely, max 20%). In other words, the battery will still hold substantial value and when a person buys a 8-year-old Model S in the future, they are not only buying the car but they are buying the battery pack (ie., fuel savings) as well. This is why the residual value of a Model S (or another EV with a large battery pack) will be substantially higher than a comparable ICE car.