In addition to charging hourly fees on par with top Wall Street law firms, Wachtell, Lipton, Rosen & Katz routinely charges success fees that rival the fees of investment banks in merger and acquisition transactions, according to an email Wachtell partner William Savitt sent to Twitter’s in-house counsel on the eve of Elon Musk’s takeover of the company.

The firm also adds success fees between two and two-and-a-half times the firm’s hourly fees in “premium billing matters that involve substantial litigation,” according to the email.