I seriously think iTunes must be trolling IK Multimedia. Take a look at the order these apps came out.
In the same hour, between the $20 and Free versions of DJ Rig for iPad, comes an update for one of oldest free DJ apps.
For the first time ever, you can DJ with true headphone monitoring! Requires iOS6 and additional hardware such as an HDMI cable and interface or a USB Audio interface.
- DJ with headphones using HDMI or a USB Audio!
- Control your headphones monitoring mix and volumes
- Bug fixes
This is made by the same guy who did Mashup, but for $35 less and it looks like it includes some of the best features.