Revolution in The Valley, page 256, Andy Hertzfeld:
Bill Gates had Apple in a tight squeeze, and, in an early display of his ruthless business acumen, he exploited it to the hilt. He knew Donn’s BASIC was way ahead of Microsoft’s, so, as a condition for agreeing to renew Applesoft, he demanded that Apple abandon MacBASIC. He then bought it from Apple for the price of $1 and buried it. He also used the renewal of Applesoft—which would be obsolete in just a year or two as the Mac displaced the Apple II—to get a perpetual license to the Macintosh user interface. This probably was the single worst deal in Apple’s history, executed by John Sculley in November 1985.