Testing Multicast on a Private LANs?

SD asks: "I am planning to write and experiment with multicast RTP streaming. I am not sure if my ISP supports multicast at the router level, so I am wondering if there any way I can set up a LAN in my home to experiment with multicast technology." For those of you who don't know what a Multicast network is, you may want to check the HOWTO. It strikes me that building a network to test multicasting would not be something you would want to do in too small of a scale. Without more details about what kind of application is getting tested, what do you feel would be a ballpark numbers (routers, machines, etc) for a network designed for testing multicast applications, and how much would such a thing cost?