That's on the supply side. Many items with a limited/fixed supply (land for example) are operated under capitalist principles. So why do we not allow people to

That's on the supply side. Many items with a limited/fixed supply (land for example) are operated under capitalist principles. So why do we not allow people to sell their own organs? Or eggs and sperm? Or rent out our womb, or sell our hair? Do we not have sovereignty over our own bodies?