If marijuana taxes are found to be too high or the taxed overall price comes out too far over what the current black market prices are, then yes, the black market sales will continue. No one wants to overpay for a product that is only worth a set market price.
Yes, higher marijuana taxes will increase black market sales. It is no surprise that when anyone wishes to purchase something, they will attempt to find it at the cheapest price, it is only logical. With a substance that's already under control from government laws, an increase in it's taxation would only boost underground sales of said product. People will seek out the cheaper purchasing alternative, even if involves dealing under the counter.
People buy tobacco products and alcoholic beverages even though they are taxed at a pretty high level, so they are going to buy pot when it is taxed, too. There is already such a huge black market for pot that most law abiding people would be happy to have a legal venue and pay the tax.
Currently most marijuana sales are black market sales so the legalization and taxation of marijuana will initially lead to an increase of taxable marijuana sales. Once there is a federal legalization of marijuana there will be many people who will be willing to pay the inflated prices in order to use the substance legally.
Many states already have high "sin" taxes on cigarettes and alcohol and people might complain about the steep prices but they still buy them and many people just accept that is how things are.
There are stores that sell alcohol after hours and cigarettes tax-free, but that doesn't mean sales have increased on those. There will be a bit of difficulty getting highly taxed marijuana to catch on at first because of its prevalence in the black market, but when you can walk down to the store instead of being forced to wait on a delivery or go across town to see the one guy you trust, everyone will take the five dollar hit.
No, I don't believe that high marijuana taxes will increase black market sales. The taxes on cigarettes and alcohol are fairly high. With that being said people still bite the bullet and pay for these items. If a person can purchase an item legally without any consequence, minus the high taxes, they will most likely be glad to do so.
No, I don't believe that high taxes on marijuana will increase black market sales. Black market sales on marijuana right now make up 100% of sales in states that have not legalized it for any type of use. In these states, should marijuana become legalized, the black market dealers will be all but forced out of the business, because manufacturers will be able to provide it for very cheap. Of course, high taxes will somewhat even out the price, but it would still be quite low compared to black market prices of marijuana, and once marijuana is legalized everywhere in the U.S., for recreational use as well as medicinal, the black market will vanish and prices will be at an all time low.
Higher marijuana taxes will not increase black market sales, rather promote the formation of local growing cooperatives that rely on community resources and care. Since it would no longer be a limited supply due to legality, and no longer need to be trafficked form foreign producers, the ease with which these coops could be formed would essentially limit the black market.