There are a few obvious and not-so-obvious causes of a large content folder, even after declining updates and running the Cleanup Wizard:
- Downstream servers. If you have downstream servers, then you won't be able to get rid of the updates unless every single client on every single downstream server shows it as unneeded, regardless of approval status on the upstream server.
- Express Installation Files. If you've enabled these (under Update Files and Languages), then your content folder will increase in size by a significant amount.
- Other languages. If you have more than just English updates selected, then you'll see an increase in language-specific update files.
- Forefront client updates - These are big. Really big.
How many updates do you have, by the way? For us, with about 1500 approved updates, the WsusContent folder is only about 16 GB. The SP and services folders are an additional 2.5 GB.