You may find my previous answer on the cost of armour in 15th century England useful. Ultimately, this is a counterfactual question - medieval monarchs did not have the money or the centralized organization to personally equip an army that large. When we look at the numbers of armours (generally partial armours) provided by monarchs in the Middle Ages they are in the low thousands, and supplement equipment brought by the soldiers themselves, or provided by lords or other employers. 40,000 men is rather large for a medieval army, as well! I talk about the overall logistics of armouring a late medieval army here.