Really good point there. If Uber can charge $1.01 for something it pays $0.99 for, then it might have a sound business model. But if it's in a perpetual state of offering discounts down to $0.98 to keep users buying rides, then it probably doesn't, and to relabel the underpricing as a marketing effort is just obscuring that.
Hiding $1800m of ride discounts under Sales and Marketing feels deceptive. If a store advertises "summer sale, 30% off!" for a month, you can reasonably call that marketing spend.
Uber is different. If my flight's leaving in 1h30m, I pull out my phone, open Uber, type in LAX, open Lyft, type in LAX.
Say Uber is $17. Lyft is $20. I pick Uber. If there's a "promotion" going on under the hood to produce that $17 number, is that marketing? It's really just price competition in a cutthroat, negative-unit-economic market.
Given that, Uber laying off 400 people has a dual effect. It's cutting sales spend. It's also creating news to distract from the fact that >50% of the sales spend is really per-ride losses.