Recently the question was asked:

How does BUILDER determine which items to fund (budget) when items have an identical score and there are insufficient funds to cover them all?

The answer provided by Dr. Mike Grussing:

As far as budgets and the priority score is concerned, BUILDER uses a greedy algorithm approach to fund prioritized work items, as it tries to allocate as much of its budget in each year.  So it ranks the work items in descending order in terms of priority and then in terms of cost.  Then as it moves down the priority list of work items, and gets to a point where the next work item to fund is more than the remaining funds available, it will skip over that and try to fund the next item on the list until it finds an item that is less than the remaining funds.  It keeps doing this until all the funds are expended or it reaches the end of the list.