If that R&D doesn't pan out they essentially will go bankrupt quickly as their R&D spending was 81% of their revenue.
Rated by Moody's as B3 and by S&P as B-, which is the bottom of "Highly speculative": https://en.wikipedia.org/wiki/Bond_credit_rating#Credit_rati...
For comparison, Uber bonds are one grade lower than Argentinian bonds: https://tradingeconomics.com/argentina/rating
Such credit ain't cheap, especially now that interest rates are no longer zero.
and the lowest paid engineers at Lyft are probably ~300 total comp.