I see the concerns that you have, but this is not that unusual behavior. When someone logs into the Administration backend, there are lots of things that initialized. While we can clean some of them after the usage or logout, some of them continue to live in the memory during the whole process lifetime. Please don't get me wrong - there are things to be optimized, but we'll probably never get the memory as to prior to login to the backend, or as to after the startup.
The next release of Sitefinity is going to bring some pleasant surprises to the memory usage especially the performance. Stay tuned...
..and Happy Holidays :).
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items