We all know that Sally was, for lack of a better word, an idiot for selling seashells at the seashore of all places. Do you think if she had made better choices in life that she may have been a more successful business woman? I mean her family was certainly well off and she had quite the lucrative business idea (if the current puka shell necklace trend is any indication) so why didnt she just set up shop as a fashion designer? She was on the cutting edge of what could have been the precursor to the iPhone in terms of "the next cool thing" and would have certainly had the base cash necessary to start advertising and getting the ground floor ready.
Principally for the reduced transport costs and tax avoidance.
What you have to understand is that the means of getting this product to major inland marketplaces involved carting live shellfish over toll roads. And that the greater volume of transported goods consisted of the shells and some seawater to keep them alive.
She massively reduced costs by transporting only the meat. This reduced the freshness of her goods. But accomplices bidding high on "air-cured oysters" convinced consumers that these were luxury goods.
Meanwhile, she posed as an impoverished coastal shell merchant to escape the attention of the king's treasurers. In fact, she would often give-away the residual waste-product for a penny-a-ton.
Tl;Dr . . .
She selfishly scored shillings shilling unsafe unshelled shellfish.
She assured such scam by seemingly selling seaside seashells, but selflessly sharing surplus shellfish shells. .
You may as well ask how Peter Piper could possibly pick a peck of pickled peppers, given that it is impossible to pickle peppers before they have been picked.
Actually, Sally went under the radar after that embarrassing incident, but she actually did go on to find some success as a saleswoman. I've heard that she sold snow to an eskimo, steaks in a vegan colony, and water to a drowning man. Unfortunately, she was charged with first degree murder in relation to that last incident, and died while in prison.
Well, no. Sally was selling seashells at the Seychelles. The "seashore" is actually commonly understood to be a mistranslation by American historians who translated the story, which was originally recorded in British.
Sally was mainly involved in the mining and exporting of seashells. The Seychelles are home to some of the largest seashell mines in the world, an industrial good that was very scarse in much of the world. Sally's Seashells was one of the largest companies in the world before it was forcefully nationalised to fund the failed Seychellian invasion of Marocco.
Mods should remove this question; it's far better suited for /r/AskEconomics