How much money they've spent in the past is irrelevant. That money all came from investors, in exchange for a stake in the company. It never needs to be "paid back". Besides which, those investors have earned all those funds back already, and then some (on paper).

All that matters at this point is how much money they'll lose/earn in the future. There are no shortage of investors willing to put money into this effort, and they're growing exponentially, so there won't be any pressure for them to turn overall profitable for several more years.

Boeing may never make back the development costs of the 787. That was an absolutely epic disaster of a project. But that doesn't mean Boeing shouldn't build and sell every 787 they can profitably sell.

If Waymo is at breakeven including capex, opex, and overhead, operations logistics becomes the limiting factor. While Alphabet is capable of investing more money into Waymo, I think they've reached the tipping point. If you see Waymo expansion accelerate, bet on that tipping point having been reached.