Revenue from a post-280E marijuana tax: Gross and net

I’ve written that federal and state revenue from taxing marijuana could be as much as $25 billion a year. http://www.huffingtonpost.com/pat-oglesby/a-way-marijuana-dilemma_b_2490720.html.  But a revenue estimate for a new marijuana tax would presumably involve revenue loss from repeal of unpopular section 280E, which disallows deductions for all expenses other than cost of goods sold.  Repeal of section 280E could be costly.