Hello there!
I'm a graphic designer who works on a book that would serve as a guide for artists how to understand armour. Many people create art that's unintentionally ridiculous, giving birth to many misconceptions and myths. Quick example would be a scene from LotR: RotK, where Faramir goes back to Minas Thirit with an orc arrow in his breastplate.
I wanted to include a paragraph in which I'd explain how to judge a value of a popular armour (let's say chainmail and Milanese full plate) and maybe compare it to a price of a car. I've found one guy online who did that here:
Since plate was used for a relatively short period I think this question is answerable.
In general a full harness cost as much as the yearly salary of a craftsman. Converted to todays prices that’s about €20–25k. That’s a relatively cheap family car.
We know that in London in the 1450s a full suit of Milanese plate set you back by £8, the minimum yearly income for a nobleman being £40 (could go up to a few 1000), well off merchants and civil servants could get as much as £100/year. The avarage thatcher of a village in this period had an income of £8–10/year. The income of the crown being yearly £25 000.
I don't want to base my claims just on a random post. Could you please recommend me a credible source where I could easily access similar information? I've already wasted several hours trying to go through my books, just to find multiple accounts of varying prices, just to ultimately find out that the measure used was "grzywna" that meant different things in each substate of my country (Poland). ._.
I don't know if this is at all helpful to you, but I've done a quick dive through a few of my sources and come up with some information. I do 11th-13th century, not 15th century, so this is for the armor of that period. All of our evidence is essentially anecdotal; when a source gives us a price for something, it's very difficult to know what that means exactly, because we don't have other values to compare it to.
First, John France in Victory in the East: A Military History of the First Crusade gave a value of 100 sous for a mail hauberk in 11th century France. The hauberk was the premier torso armor of its day, and in addition to a helmet, all the armor a knight of that time commonly wore into battle. The sou was equivalent in value to the medieval English shilling, being 1/20th of a livre/pound. So, 100 sous would work out to be 5 livres. Or, as John France says, the value of more than ten oxen or as many as five horses, or one free peasant's farm.
Next, Michael Prestwich analyzed the records of the English royal household as part of his book Armies and Warfare in the Middle Ages: The English Experience. He gave varying prices for armor in the early 13th century: a pound for a hauberk, a mark (2/3 of a pound) for a haubergeon (a shorter mail coat), and ten shillings for an aketon (a thick cloth armor). A skilled laborer might make between two and eight pounds a year.
Now, it's very difficult to know exactly why basically the same mail garment cost five times less in the early 1200s than it did in the mid-1000s. One could have been higher quality than the other, or in better condition, or any number of factors. But I suspect it also has something to do with the growth of the European economy in the intervening centuries. Western Europe underwent a tremendous metamorphosis between about 1000 and 1300 AD; the population tripled, while the economy grew more than apace. I would imagine the arms industry also grew during this time, churning out more and more material at lower prices.