make your medical insurance companies pay for legally prescibed medical marijuana

It has been proven that various types of medical marijuana help those with chronic pain,cancer,copd,heart desease and debilitating arthritis and other diseases that no other drugs seem to help. The cost of getting prescibed medical marijuana is beyond most people's ability to pay and the payment must be in cash so I have heard, Yet doctors can prescribe the horrible drugs that become addictive and insurance will pay for those!!