When your visitors and customers see a product they badly want, they will of course purchase it readily. But if it is a product that they want for a bargain price, they may not buy it at the price mentioned. Again, if the price is accompanied by the regular price as well as the sale price (discounted) the buyer will be tempted to buy it any way.
This is a great feature that allows you, the businessperson, to play longer on the minds of your visitors and customers. A bargain is a bargain and those visitors who chance upon one for a product that they want will grab it with both hands.
This feature sits right on the product page; it allows you to display the regular price, sale price, and the difference between the two in terms of both percentage and dollars. A nifty little must-have feature!
