I posted the same question a few days ago. I didn't get any replies but here's what I've been able to determine on my own (under Mac OS) and from the documentation:
A basic standalone has grown from around 30 MB (Max 5) to 100 MB (Max 6).
When you build a standalone, your patcher is saved as a collective along with the Max 6 runtime application and other frameworks and resources. The executable binary in Max 6 runtime has grown in size: 27.3 MB (compared to 12.7 MB under Max 5). Unless you have a friend at Cycling '74 who could give you a custom compile of a lightweight Max, you'll just have to live with bigger standalones.
Two things, however, can help reduce the overall size up to 60%, depending on what your standalone needs to run:
**Save 50 MB** Include the standalone object in your top-level patcher and in the inspector, disable anything you don't need. Consider extensions, database, MIDI support and audio support.
**Save 12 MB** Control-click on the application to *Show Package Contents*. Consider junking any frameworks you don't use, like JitterAPI.framework, MaxLua.framework and (possibly) libmozjs185.dylib (I assume it's safe to remove these frameworks if you don't access them – I have my doubts about libmozjs, though).
Anyway, those two steps alone reduce your standalone to under 40 MB. That's about as good as it gets. Still too big? Well, a fully stripped standalone under Max 5 would be ~20 MB. You could also consider stripping out some interface files but that's only going to save another 1-2 MB.
@Chris Rolfe: Not adding much to the knowledge on this topic, but I definitely posted a reply to your previous question. Just wondering if there is some kind of issue on the forum or maybe you just missed that. FWIW It happened about the same time the ordering of forum posts was all out of (temporal) order (for at least some users).