I think that this isn't something to be very concerned about. Why? The memory usage doesn't seem to scale very much as the application's size increases.

I've just written a test app that uses MSXML components, a Memo component, a couple of buttons, and a treeview. This program creates a DOM structure in memory, and displays structure in the treeview. All in all, it uses about 4.8 MB.

If I were you, I wouldn't be too concerned with a 3 MB memory footprint, but that may be because I come from a Java background