From the S-1:
"USE OF PROCEEDS
Registered Stockholders may, or may not, elect to sell shares of our Class A common stock covered by this prospectus. To the extent any Registered Stockholder chooses to sell shares of our Class A common stock covered by this prospectus, we will not receive any proceeds from any such sales of our Class A common stock."
From Uber's S1:
"Cost of revenue, exclusive of depreciation and amortization, consists primarily of Core Platform insurance expenses, credit card processing fees, hosting and co-located data center expenses, mobile device and service expenses, amounts related to fare chargebacks and other credit card losses, excess Driver incentives, and costs incurred with carriers for Uber Freight transportation. Core Platform insurance expenses include coverage for auto liability, general liability, uninsured and underinsured motorist liability, and auto physical damage related to our Ridesharing products and Uber Eats offering. Excess Driver incentives are primarily related to our Ridesharing products in emerging markets and our Uber Eats offering. [...] As trips increase, we expect related increases for insurance costs, credit card processing fees, hosting and co-located data center expenses, and other cost of revenue, exclusive of depreciation and amortization, categories."
Cost of revenue was in 2018 $5.6bn (out of $11.3bn of revenue). The also provide "adjusted net revenue" excluding among other things excess Driver incentives and Driver referrals: in that case the cost of revenue is $4.3bn out of $10bn.
Uber's gross margin is below 60%.