Many hosting companies are now using these types of payment plans. Basically, it is a labor fee for the transfer or setup of your new account with them. Some companies do not have setup fees, but they make up for this in other areas, such as raising their monthly rates or by offering less features in a given plan. For example, on the computer you are using now, it has a certain amount of disk space on its hard drive. One of your programs on that computer may take up 15 MB of storage space on your C drive.
Web hosting companies' servers work the same way.
They allow each of their customers a certain amount of disk space to store their web site material on, such as images, HTML files, emails, etc. 125 MB is a very large amount of space for a web site. Most web sites only take up 3 - 10 MB, if that. It is actually the 'transfer' of the data that you see in front of you. But most of the sites that offer unlimited data transfer also have rules in place that prevent customers from abusing their system.