[caf]

It seems to me that they are using an expected lifetime (in the "expected value" sense) of 200,000 km for both types of vehicles.

If those factors apply equally and dominate the reasons vehicles reach EOL, then the expected lifetime not varying significantly between the vehicle types looks like a reasonable assumption.

Using the real expected lifetime taking into account the circumstances that tend to render a vehicle permanently unserviceable in the real world looks like the correct approach to determine how manufacturing costs are amortised over the vehicle lifetime.