You can, they are called a petrol station or Bottle shop, high volume will not attract 100% mark up, as for LHB's they have to try and make the 100% they can't import themselves because they could not sell the amount they are importing so have to rely on a body that imports, hoping that will give them a profit, believe me there is not a good income to be earned being a LHB shop, there are the stand outs like Grain and Grape, but to many equals to much competition.
Some will think by undercutting the opposition they will make more money but the sales have to be huge, it doesn't work that way.