The dialog box for tasks could have the option to select a recurring task. The duration of the task would then be repeated, depending on the selection (weekly, monthly, yearly, etc.) The cost assigned to the task would be for the the entire task, and not each part (although, this could also be an option in the dialog box). 

Personally, I am not so concerned about the cost(s) associated with the task but I support the addition of Task Recurrence options.