I'm curious to see how much money went where in the medieval governments of Europe, but I'm not even sure where to start looking.
If the British Isles are within your range, the Pipe Rolls survived in a continuous series from 1155, with some earlier ones also extant. The UK National Archives has information online about how to access them. The Pipe Roll Society is dedicated to publishing them.
Unless you're a Latin scholar, you'll want to access someone else's research into the rolls to get the kind of information you're looking for.