Jennifer Aniston earns more from Friends reruns every six months than Sadie Sink earned from ten years of Stranger Things. Sink's final season paid $7 million. Aniston's show ended in 2004 and still pays her roughly $20 million a year. The gap between those two careers explains the entire economics of streaming. Old network TV paid actors modestly upfront and let syndication make them rich. The six Friends leads negotiated 2% of backend revenue in 2000, and reruns have paid them like annuity…