A tax is imposed on marihuana and controlled substances as defined in Section 40-17A-1 at the following rates:
(1) On each gram of marihuana, or each portion of a gram, $3.50; and
(2) On each gram of controlled substance, or portion of a gram, $200; or
(3) On each 50 dosage units of a controlled substance that is not sold by weight, or portion thereof, $2,000.