You point out a lot of good reasons why people look for alternatives to Dropbox and similar online syncing and storage services, including added security risks and costs when you’ve got a huge amount of data to sync up. Some workplaces and campuses don’t even allow Dropbox or other external servers to be used at all, for intellectual property reasons or, again, security.
So what can you do? Thankfully, there are several tools you can use to sync your computers directly, bypassing the need for you to use an online server as a middleman. Here’s an overview so you can choose the best one for your needs: