Broadway Flash said: "Do we know how much upcycling of sceneryand costumes is going on? Why don’t they build a cleaner place in midtown. Wouldn't that be easier for everybody? And much less gas."
There's no straight answer to this. It's going to vary show to show. Cost, appearance, and practicality are the sole major factors when building a show. Unless there's government legislation or extreme tax incentives, "upcycling" is never going to happen on a massive scale.
Sometimes entire packages of scenery/props and costumes get saved and rented out or purchased after a show closes, if an agreement between the producer, the union designer, and others can be made. There's your upcycling.
Theatre people are meticulous on Broadway. Designers and directors have extremely specific ideas about how things should look. That's their job.
Regional theatres do a lot of repurposing for budgetary reasons (repainting lumber, saving hardware and using it until the screws are stripped, reusing costume assets that they own, having a Props Storage). They can do that because they own these things and have a place to store them. A Broadway show is a startup and a musical is being built to last many years.
I don't know what you mean by "build a cleaner place" or who "they," is but drycleaning occurs primarily 10 miles away in the Bronx via Winzer Cleaners, which offers the best rates & level of expertise. Anything occurring in walking distance from the theatres is going to skyrocket because of rent costs. And large/heavy things would still probably have to be trucked.