The financial drain from France to the Regno will have affected more Frenchmen than any other aspect of the enterprise begun in 1265. Conquests come expensive, and conquerors naturally try to put the costs on to as many shoulders as possible. In their efforts to exploit all conceivable sources of revenue, Charles of Anjou and Charles II were aided by the pope, by various Italian bankers, and by a small number of faithful French lords. France could not be made to pay as much per head as Provence or the Regno; but it was squeezed in every feasible way, often with the support of the crown. So great was the effect of the initial outpouring of capital from France for the expedition of 1265–66, both in terms of ecclesiastical taxation and in terms of the money individual crusaders brought with them, that this flow has been seen as a factor contributing to the decline of the Champagne fairs, which had been the focal point of most French trade with Italian merchants since the second decade of the thirteenth century.

The initial victim of the financial drain was the French church. As a condition of attempting to eliminate the Hohenstaufen from the Regno, Charles of Anjou was promised in 1264 by Urban IV a tax of a tenth on the property and goods of the French church for three years.