Big Bird made a foray into business a long time ago. Have you been to a toy store lately? Sesame Street takes up a whole department. Why can't the profits go to supporting PBS. After all every other product supports it's own shows.
I think the profits from these toys DO go back into supporting PBS and the show.
The problem with the model is we don't want the Sesame Street Gang becoming the Teenage Mutant Ninja Turtles, who only really exist to sell toys and provide no other value.