When testing anything on a computer, you have to take a running average. Peak memory usage will change based on what resources are available at the time. If you are truly interested, I recommend using the Red-Gate Tool
Ants Performance Profiler.[
^] I use that in house to look at my code. It does memory along with testing the execution times of all lines of code. It quickly showed me places where we needed to improve our code.
I don't work for Red-Gate, I just like their tools. Hope this helps you out!
Hogan