I often hear that plate armour eventually became cheaper than mail armour, but I also hear it otherwise. And as far as I can see, both sides have their arguments - but what is the truth? Did the price vary depending on your location, i.e; would plate armour in Milan or Augsburg be much cheaper when compared to plate armour in, say, England?
I'm hoping for info from the 15th century.
At least in the Burgundian accounts, the mail armour is cheaper (in general) as the plate armour, but some very high grade mail armour could be a lot more expansive than low quality plates armour. For exemple, a full plate armour could cost between 37£ 3 s and 76£ 10s, a mail shirt, between 5£ 13s and 50£, a higher price than the lowest prince found for a full plate harness. (Those accounts spoke about livres tournoi, tournoi pounds, and not Sterling).
This variation in price is also found in the inventories of the armory of the tower of london (second part of the 14th), as Thom Richardson prouved in its thesis, where you could find mail shirts (iron) between 16s 1d and 46s 8d, and mail shirt made of steel, at the price of 4£. (Iron and steel are not always related to the use of proper steel or iron, but could aslo be use to note the quality of the armour)
Sources: Burgundian account, in AGR (Bruxelles) and ADN (Lille).
ROBCIS Dominiques, armes armures et armuriers sous le principat de Jean sans Peur (1404-1419) d'après les documents comptables, Paris, 1998.
RICHARDSON Roland Thomas, The medieval inventories of the Tower armouries 1320-1410, PHD Thesis, Unversity of York, 2012.