Every time a 2 MB site is downloaded, or visited, your hosting company counts up 2 MB of data transfer. Thus a 2 MB site visited 500 times in one month racks up 1000 MB of data transfer. Most companies will limit the free total data transfer, after which you are charged by the MB for the rest of the data transfers, or hits. Hosting companies which charge low for monthly site hosting may charge big-time for data transfer after a very small amount of free data transfer. No Limit on Data Transfer.
Larger companies charge more to cover the high costs of personnel and overheads.
Hosting on a state of the art Server.