If I make a widget for $100 (50/50 fixed, variable) and sell it for $90, I've covered the variable costs. But If I only have one line, all those fixed costs are attributable to that one line, so its still not making a profit.

If you had multiple lines and one line that wasn't making a profit, but was making a contribution to fixed costs, it maybe better overall to keep that line in place. That isn't what we seem to be talking about here, but it depends how 'fixed' the fixed costs are.

What does that mean?

Uber revenues minus cost to operate Uber car service = $940 million in 2018.