Is it permissible for a disabled person to sell their "Medical Commission papers" (customs exemption certificate) to another person due to their inability to buy or afford a car, knowing that the state only exempts them from customs duties and does not bear the cost of the car?

It is not permissible to substitute the right of a disabled person to customs exemption, because this right is granted to the disabled person exclusively, and thus he does not own the right to transfer it to any able-bodied person, whether for compensation or as a donation. This is also because customs duties are mostly imposed without right, and therefore it is not permissible to take compensation for their waiver.