The black market would not get involved, at least if the states weren't braindead enough to tax the product differently from state to state. Why would they? The only reason they are in tobacco is because taxes vary from state to state, so it's easy to buy cigarettes in Virginia and sell them in New York. But if pot was taxed relatively the same in all markets, there would be no incentive for them to get involved. Right now the black market sells their product for $300-$400 an ounce, and they pretty much make it all in profit, the exhorbant price reflecting the risk of operating in a black market. In a legal market, they are going to have to sell the same ounce for $10-50 or so, and have to compete with someone going to a store. If there is any black market involvement at all, it will be a blip, much like it is with tobacco. I doubt less than 10% of tobacco consumers get their product thru the black market.
Centralized government.
Here you just went through an explanation of how cigarette taxes were different in every state, then you turn right around and assume pot wouldn't be treated that way.
Your $1 pot with the $99 tax invites the black market. They won't sell it to just another state -- they'll sell it anywhere tax free. With that kind of profit, hell, I'm tempted.
People are willing to pay $5-10 per gram for legal pot in Amsterdam. Why would anyone sell it for anything less? Do you believe that the voters in this country want to legalize marijuana and make it available for $1 per ounce?
You're all caught up in this notion that since legal pot can be cheap it will be cheap. Government licensing, taxes, product liability insurance, etc. will drive up the price way beyond what it actually costs to manufacture.