These pot tax calculations always assume the price of pot stays what it is and everyone pays the tax. Once pot is legal to grow the price will plummet and almost nobody will pay the tax. There may be other reasons to legalize pot, but it won’t generate a billion a year in taxes.
I know this may ruffle some feathers around here, but I’ve always been for legalizing pot. It seems a bit hypocritical to me for society to have a bar/liquor store every other block but waste so much time and cost on busting people who smoke marijuana.
As far as the tax base goes, however, I agree...this will not be a good source of future tax earnings.