Ok, that's a fair point, although it was not implied that Tesla will not improve efficiency, it was just a quick illustrative calculation.
They've been cost-cutting very aggressively so I assume there are few low-hanging or middle-hanging fruits left.
The big picture is that their business is currently not profitable without government money, which doesn't scale linearly with revenue. Sure, I guess they will slowly improve their margins in the future. But my point is that it's unlikely that their car manufacturing business will become a massive cash cow as the market seems to think.
Batteries becoming cheaper won't directly translate to margins because of competition.