Let's say you're shopping online (on a NopCommerce site) and you find a product you like. It's listed for $50 and you add it to your shopping cart, but you don't check out (or your browser/computer crashes). That evening, the admin changes the price for that product to $100. The next day when you go back to your shopping cart to checkout and pay for the item, you now see that it's changed from $50 to $100. At that point, you get upset, close your browser, and vow never to come back to that site/store again, just because the prices changed after the products were already in your cart.
You can create or imagine several hypotetical cases and scenarios like this, which have a very little probability of happening in real life.
You can create another which occurs more often: when you are controlling inventories and two customers are allowed to add the same last item to their chart because at that time inventory= 1. Normally e-commerce systems decrease inventory when the customer conclude payment process, so it may happen that both customers pay and inventory ends= -1. I can tell you many more that do happen in e-commerce.
The best is to be open when this kind of special situations arrise, to solve them manualy ona a case by case situation.
