It is common for those doing a transfer to another member to require payment before the transfer is actually done for the obvious reason that once a transfer happens it cannot possibly be reversed, and thus the transferor cannot get the points back if the transferee fails to pay.
Doing a transfer for money mainly relies on the honor of both participants and many such transfers occur. One could draft a contract, and probably some have, but that may provide no protection to either party. DVD/DVC will not do anything to protect either party if any transfer agreement for money is breached, and it is highly likely that bringing a lawsuit if things go wrong that a court would provide no relief. That is because the POS documents expressly prohibit doing any transfer for money, and courts generally will just leave the parties as they are when an agreement to do an invalid act is at issue.