"The investors will also get warrants that can be converted into shares with a valuation for the company of $18 billion, a drop of almost half since Airbnb’s la

"The investors will also get warrants that can be converted into shares with a valuation for the company of $18 billion, a drop of almost half since Airbnb’s last fundraising in 2017, the people said." This indicates they'll get twice as many shares for the money as previous investors. Hence a ~50% drop in valuation.