Ford makes $776,348 per employee. I will take a stab in the dark and say that the assembly worker is making substantially less than that regardless of whether it is $20k or $100k car while still producing far more value than the cost of either vehicle.
As already mentioned, that is revenue, not profit. If you take $1000 worth of material (costs) and make something you can sell for $2000 (price), then you've created $1000 in value, not $2000.
My point is that the value created by a worker doesn't define the salary (although it creates a cap, you can pay more than value created).
A great example are lawyers. With the glut of lawyers out there, a lot of lawyers are getting paid less than $50K/yr. I would argue the work they do is worth more than that, but since there are so many lawyers chasing so many jobs, salaries fall.
That is revenue. Revenue per employee can be a useful measure, but usually it's better to look at net income since industries have varying levels of expenses. Ford's net income in 2015 was about $40,000 per employee. That's healthy, but low enough, when you consider that multiple employees and systems are involved in the design, production and sale of vehicles, that the less profitable vehicle lines need to be cost controlled to stay in production.
http://csimarket.com/stocks/singleEfficiencyet.php?code=F