- Market cap: 50B
- Expected return on capital: 10%
- Expectable profit margin: 10%
- Expectable average unitary price: 50k
50B*10%/10%/50k = 1 million vehicles.
Tesla is selling about 80k vehicles yearly (at about double the above average sales price): http://www.ibtimes.com/tesla-motors-tsla-1q-2016-sales-14820...
The current valuation requires an increase in volume of five to ten times. Given the sales volume evolution of the current product lineup and the entry in a lower segment, it's definitely not out of reach in a five year horizon. Add up to five years to pay accrued debt (it should amount to about 10B before Tesla reaches steady state in the known product lineup).
All numbers are order-of-magnitude precision, but they surely do not point to a «certainly "wrong" stock value».