Many serfs could not legally leave the land they were attached to and did not have freedom of movement. Part of the value of that land when it was sold or trade

Many serfs could not legally leave the land they were attached to and did not have freedom of movement. Part of the value of that land when it was sold or traded was the serfs bonded to it. This shouldn't be particularly surprising because even some knights were owned by Lords and could be traded or given as gifts to other Lords.