Rocksmith 2014 is on sale for US $12.48 (75% off) in the Humble Store. RRP is US $49.95.
The lowest price at other places is US $19.60 right now: http://cdkeyprices.com/product/Rocksmith-2014-CD-Key-Steam. Note that you'll also need a Real Tone cable, which can be bought for around $35 from ebay.
Sale ends 1AM Sunday 14/09/2014 AEST.
Some sales blurb about Rocksmith 2014 itself:
Rocksmith® 2014 Edition is the fastest way to learn guitar. Plug in any real guitar or bass and join over 1 million people who have learned with the award-winning Rocksmith method.