Todd,
Not sure if this will answer your questions or not but here goes.
1. There is no "cut and dried" price for a Symposium agent. Mom and Pop will pay twice that as a Fortune 500. And, most likely, no one here will tell you what they pay since they either don't want you to know that information, or if they are like me, they don't write the checks, they just make the systems work.
2. If you look in your Historical Statistics, you will see two variables under Parameters. One is Active Agents, and the other is Agent Positions (phoneset). The Value under Agent Positions (phoneset) is configurable. You can build up to 6000 phonesets in the Symposium. The value under Active Agents is hard set. This is the actual number of simultaneous agents you can have connected to the Symposium. This means that if you ran a Call Center that had three shifts with 100 agents on each shift, you could create 300 phonesets, but only log them in 100 at a time.
If you have the capacity in your switch, and excess licenses at any given time, then you can simply create the added phonesets for you training lab and log them in as appropriate.