pinski
Not Ludicrous
In my initial post i mentioned that it won't depreciate except wear/tear and maintenance costs which is very different from depreciation based on model years. Because people will pay a premium for a new car when it is for personal use, a one year old car must have a substantial discount and then a 2 year old car must have a further discount to a one year old car etc. That leads to usually about 50% depreciation in 3-4 years.
When depreciation is based on wear/tear and maintenance, it's very different. In your scenario the car is fully depreciated after 3 years but that assumes 300,000miles driving. If the Tesla Network is available in 2019, 3 years later would be 2022. By then a 60kwh battery replacement probably doesn't cost more than $6000. If you replace the battery every 300,000 miles as you suggest, that's 2 cents/mile. Re-upholstoring the seats and fixing wear items shouldn't cost much more than that so probably an additional 3 cents/mile. In total that's 5 cents/mile. Using your assumption of 20mph average, that's $1/hr to cover all those costs. Add in electricity and Tesla's percentage and I think it's quite doable to initially net $2/hr after accounting for all that. Even at a gross price of $4/hr, the Tesla Network would be 1/4 the cost of Uber.
Interesting topic and interesting read through the comments. One thing to consider, that I think Chad may have been alluding to, is that ICE vehicles are generally junked after racking up so many miles, 300k in our example here. It won't just be the powertrain that fails during that time period, it'll be the interior as you mentioned, steering components, suspension components, HVAC components. Those costs will add up incrementally to the point where another Model 3 is a better option than fixing the high-mileage one.
I'd be really interested to see if Tesla is doing any torture testing for the Model 3 where it's in relative constant use 12-15 hours a day. Some components have more of a time-constraint with regards to degradation and will probably be fine during our three year example. Others, with a direct mileage correlation, probably will need either frequently serviced or replaced.