This one day only event will feature almost all smartphones and tablets for $49.99 or less after a mail-in rebate with a new two-year service agreement on any Unlimited Value plan with a 2GB for higher data plan. Existing customers who are at least 18 months into their contracts are also welcome to upgrade their plans in order to take advantage of the sale.
Some of the devices in the $49.99 bracket are the Samsung Galaxy S II, HTC Amaze 4G, HTC Radar 4G, BlackBerry Bold 9900 4G, and the T-Mobile G-Slate. Additional devices and prices can be found on the T-Mobile Magenta Saturday Sale promotional webpage.
source: T-Mobile via SlashGear