I would agree that overhead and volume has a big part in the prices, however, taxes and tariffs play a big part as well. You have the supplier that had a tax increase, (pretty much every year), and that increase is passed on to the distributor. The distributor also has had tax increases on the tobacco he brings into the State, (in this case, I am going by Virginia State laws as they are the ones that I am most familiar with). The distributor then passes that cost on to the retailer. The retailer also gets hit with a tobacco tax on any tobacco product that he sells. That's a triple whammy on all tobacco that the retailer sells. I have watched as bulk tobacco prices went up a buck twenty an ounce in one day, (July 1st in Virginia when new laws are enacted), and it was all due to passing on the tax increase(s).
As far as some online retailers charging taxes, if you have your base of operation in Virginia and you sell anything to someone in Virginia, you charge them the sales tax. (From my understanding, it works that way in pretty much every State) Other online retailers went through this headache a few years back and have since developed software that will charge the sales tax to which ever State they are shipping to. They are also responsible for paying that State its taxes owed from the sale. The tobacco online retailers are getting ready to experience the same headache and ultimately will have the same outcome. We, as the consumer will feel the effects when that happens. The price for having to do the extra work, (i.e. overhead), will be passed on. It will be the only way to keep operating.
Now, the online retailers do not have many of the overhead costs to deal with that the B&M's do, and the prices will still remain, (in all probability), lower than what your local B&M is charging, but I don't think that we will see the large difference in prices that we see today.
Still, I will continue to shop both online and at my local B&M. I think that the B&M's still have a lot to offer even if the cheapest price isn't one of those things.