A webplayer build that has a scene with a cube and 3 point lights is 50K. Look in the log to see what stuff you're including. For example, all scripts and everything in Resources (if it exists) is included regardless of whether they're used or not.

What kind of build do you have created? When you create a web-build you can see the detailed memory usage in the editor log. Just click the small button at the top right of the console window ("open editor log"). If you search for "***" you will find the line ***Player size statistics***.

"normal" standalone builds work different. They aren't that strong compressed. I just created a webbuild of my test project with some scripts and some prefabs but no textures or mesh data. It creates a unity3d file of 45KB.

The standalone build is much larger of course ;) since it have to include the whole engine ... something about 9.5MB + the exe (about 6.5MB)