That is a really vague question, you need to provide more information. The budget is completely dependent on how busy the site is and how much traffic you are going to be pushing. We currently have a client with ten's of terabtyes of data doing a similiar thing but his monthly expenses depend a lot on how much storage he needs.
If you are starting off small a cheap P4 or Xeon with a 500Gb drive will give you a fair amount of space to use. As you grow you will want to move to dedicated fileservers, whcih depending on your budget can hold multiple TB in a single server.
The budget also depends a lot on the datacenter that is choosen or if colocation is done, which depends a lot on how much up front cash you have. Once it gets rolling you can easily have tens/hundrdeds of Gb's uploaded in a day.