Owncloud is absolutely wonderful. With pricing of storage going up everywhere else, OwnCloud's system is the one to beat. Open source, it works just like Dropbox/Onedrive and other systems we've already used. It's quick to set up, most web hosts can handle it with no issues. You can customize your login page, your admins, and using it is pretty intuitive. If you're looking for customized storage that you control, OwnCloud will do the job well.
When first added, there were a few errors that I had to have my host sort, because I couldn't find any documentation on them for the OwnCloud. Since it's open source, it doesn't have a very robust support system.
Likelihood to recommend: 7/10
ownCloud Community Edition is available for free as an Open Source software.
ownCloud Standard subscription starts at $3,600 (€3,000) per year for 50 users.
ownCloud Enterprise subscription starts at $9,000 (€7,200) per year for 50 users.
Custom subscriptions are also available.