I could be dreaming this, but I'm pretty sure I used one of my National earned free days for a one-way van rental from MSP to MCI.

$100/day is a pretty typical one-way rate. For a van, it's usually $150. The agencies price them one of three ways: (1) "Regular" rate, big drop charge. (2) "Regular" rate plus per-mile charges. (3) High daily rate, no drop charge, unlimited miles.

It all depends on the purpose/length of your trip which one is best. Usually when I do a one-way, I can pick it up, load, drive, unload, and return within 24 hours, so I do option #3.