> The one part of this that I feel like I understand is that if you buy this vehicle you've effectively signed up for twice the maintenance expense.

Then I would challenge your understanding.

That combustion motor 1) is not running anywhere near as much as a normal combustion engine, 2) has no mechanical transmission to go bad and 3) can be tuned for a much narrower range of RPMs than a normal engine.

Removing a mechanical transmission is huge. Everything else is upside.