Just because medical marijuana is legal in Massachusetts doesn't mean it's time to toss your Massachusetts medical marijuana card! It's still worth it to register with the state. First, you won't pay taxes on your purchases. That's a 16% to 20% discount over recreational prices. That benefit alone will pay for your card in the first few trips to the dispensary. You'll also get access to higher-potency products and access to special patient promotions and discounts, depending on your dispensary.