The amount of ram used by ASP.NET depends a lot on how much is available. The way garbage collection works memory is freed up as it is needed.
There are also configuration settings which can make IIS recycle the app pool when memory consumption reaches a certain level.
I don't think using 200MB indicates excessive use of memory at all. Thats about the same on my dedicated server that has 1GB of RAM, but if it had more RAM I think it would use more of it. I'm running 8 sites in the same app pool. I'm also running both SQLExpress and MySql on the same machine, 2 of the 8 sites use MySql and the rest use SQLExpress.
What you don't want to see is any signs of memory leaks where the memory consumption just keeps going up on every page request and never goes back down.
Best,
Joe