Purchase decisions are made based on presentation and then need. The same products presented in different methods will sell drastically different. Think about this, shirt A & B are identical, Shirt A is presented in a comfortable nice store with a well dressed sales person and Shirt B is neatly folded and layed out in a street vendors trunk. At the same price, shirt A will sell better. The only difference, presentation. This too is the reason a great web store design is needed in the online world.