Atlas V can launch 8123 kg for $164 Million per a 2015 about ULA's rocket building & launch business. That works out to $20,200 per kg.
NASA's
Solar Orbiter will use an Atlas V 411 which can get 12,150 kg to LEO for $173 Million or $14,240 per kg per 2014 bid.
The
Delta IV can lift 23,000 kg for $400 Million or $17,400 per kg per the above ULA story. Here's an interesting graphic of the Delta family evolution found on Wikipedia.
Fileelta rocket evolution.png
Falcon 9 can lift 13,150 kg for $61 Million in 2014 or $4640 per kilo.
The
Falcon Heavy is expected to have it's first launch in 2016 with the ability to muscle 53,000 kg to LEO for $90 Million or $1700 per kg! Another Wikipedia graphic.