It doesn't take very long for new phones to go on sale these days, especially if you're savvy enough to check Amazon. For example, the AT&T version of the Samsung Galaxy S4 is now just $108 for new customers, or $118 for those who are eligible for an upgrade. (You can also add a new line and get the phone for $108.) Want something a little tougher? Amazon is offering the ruggedized Galaxy S4 Active at the same prices.