Dance Central Marathon Pack" for 1680 MSP ($21, 50% off) is the best deal for 14 songs. The Marathon Pack includes all the tracks from the four individually discounted track packs (1, 2, 3, 4) except for three: Missy Elliot's "We Run This," Sean Paul's "Temperature" and Chic's "Le Freak."
If you've got your heart set on any of those three tracks, you'll have to pick them up in their respective discounted pack for 640 MSP ($7.50, 33% off). There are also some singles for 160 MSP ($2, 33% off) that are included in packs or individually. Yeah, it's about as confusing as learning to Bernie for the first time.