Thank you for your interest in our service. Please note DriveHQ FTP is a complete FTP solution, so it comes with FTP client, server, hosting and web access, etc. For our pricing and group user licenses, please read this page.
http://www.drivehq.com/ftp/pricing.aspx
As you can see, we are having a special promotion. Our price is probably 5 times lower, and we have many times more features than other FTP service providers.
You do need more than 1 user licenses if you have 5-10 users. The license fee is very low anyway. Once you have a group account, you can create sub-users. Please make sure you allocate storage and download bytes to each sub-users carefully.
DriveHQ membership is required when sharing folders to other users with "write" permission. It is also necessary for each sub-user to logon with its own account.