This initial budget estimate accompanies a proposal. Carefully estimating the amount of work and resources needed to develop workable solutions is probably the most crucial step in getting funding. A high budget for one problem may also preclude addressing other important problems.
Budgets are manifestations of problems and opportunities.
Look at the budget guide for ideas. This is a rough sketch so the level of detail will be pretty low. See what other similar efforts have done and how much that cost. Borrow wholesale and add margins for changes, etc. Try to be as realistic as possible.