Amazon gets massive UPS discounts in the range of most likely 50% off or more for 2nd Day Air and then if you live in a state that is close enough to the warehouse your order is shipping from I've noticed some of my Prime orders have shipped UPS Ground and still delivered in 2 days since all of UPS services have guaranteed delivery dates. The overnight upgrade is $3.99 though instead of $2.99 and if you place an order for multiple items the $3.99 is per item.
Still, $3.99 for overnight shipping is a lot better than Newegg charging you $26 for overnight shipping.