If you include all of your 'standard' libraries in a JS app, it can be pretty big. I basically pull everything together for an Ember app I work on, and all-told it's ~3MB prior to minification. Minification takes it down to ~1.5MB, and Gzip-compression on the server takes it sub-1MB (can't recall the number off-hand). It's not that far off from what you might have in a JS-heavy app.
