Depends on the object, but overall, its true. We have a lot of stuff that the future might not understand which will give them something to research. Take our penny for an example. Those might be scarce if we ever stop using them, therefor a historical piece for the future.
Because a monopoly would end up making someone monopolizing the whole world to a point where no one can buy a business and would allow them to set their prices as high as they want.
