If you are looking for a hosted solution
http://www.natnetdrm.com/
http://www.drmnetworks.com/
http://www.buydrm.com/
They all charge few hundred bucks a month
If you are looking for a custom DRM solution with source code then
www.objectcube.com, but prices start at 5K
I work for objectcube, if you have questions you can email me at jay @ objectcube.com
Jay