To answer your first question: Micorsoft Silverlight has built in support for Microsofts latest DRM technology: PlayReady DRM. To set up a proof of concept solution you will need a license server and a packaging server, both of these are availible through the PlayReady Server SDK which is built upon the .NET framework. Notice: it is an SDK, not an out-of-the box server, so some developing needs to be done. To set up a proof-of-concept solution you will need the SDK, which is accessible to you after a licensing progress that can take a few weeks. For the Silverlight DRM client, all you need is the silverlight development kit, availible free online. It's hard to say how much time that needs to go into developing the license server and packaging server since it depends on how much staff that is availible to the project and the skill of your staff, but creating licenses for the silverlight client is the easiest license to create. It should not be an overwhelming project to take on. You can set up this proof-of-concept solution your self, but you will need to involve microsoft to license the server sdk.
To answer you second question: The pricing for the Server SDK is 30k $, with additional cost depending on number of processors in the license server or a small additional cost for each license that is released by the license server. So it depends on the size of your service and customer base. If you need to release a lot of licenses you will need at more powerful license server, plus release a lot of licenses.
I would also suggest looking into PlayReady service providers. These sell production-ready playready solutions to be used by other service providers that don't wish to implement a whole PlayReady solution by themselves. A list of available service providers is available from Microsoft's PlayReady homepage.
I hope this answers have been at least a little helpful, and I wish you all luck!