Cloning is not instantaneous

DR. CARY: Hancock Records wants GeniTECH to do what exactly? JOEL: Well, my boss, he... this'll sound silly, he wants to make clones of current popular bands.
DR. CARY: Ha ha, well, Mr. Dever, I appreciate your boss's ambition, but human cloning is a new science, and for starters, it's not instantaneous.
DR. CARY: Even if I were to make a clone today, it wouldn't be a mature adult for 18 years. We simply don't have the capability to do what you're describing.
JOEL: Of course, sorry to waste your time, I-- DR. CARY: What we do have are fully grown clones of every popular band from 1983 to 1985. Come, I'll show you....