Why do i get big discounts in a factory outlet?

Volume discounts. The factory outlet buys larger quantities of items, and therefore initially pays less for them, passing on some of their savings to you, the consumer.

However - at times, the factory outlet buys out a discontinued item (no longer being made) which isn't selling at normal retail. In that case, you could be buying last years model or may have trouble finding parts for an item that is no longer being manufactured.