Who paid more: Richard the Lionhearted in 1194 or Louis IX in 1250?
The Emperor demanded that 150,000 marks (100,000 pounds of silver) be delivered to him before he would release the King
The livre was supposed to be equal in value to a pound of silver.
Richard: 100,000 pounds
Louis: 400,000 pounds
That’s assuming that the livre at the time was still actually worth a pound of silver, and that the “pounds” in question were the same unit. Both may well be true, but I wouldn’t take either for granted.
And even if we compare the quantities of silver delivered, that wouldn’t mean that the purchasing power of silver was the same in both cases. Perhaps prices, denominated in silver, were lower in 1194 than in 1250? Then you could argue that an ounce of silver in 1194 was worth more than in 1250, and that therefore even the same quantity of silver in 1194 would be a higher amount of money. Something akin to the “Price Revolution” in Europe caused by the influx of American silver.
To elaborate on my last post, the Bank of England provides an inflation calculator which, in a very British fashion, goes back to 1209. So, sadly, not quite to 1194, but close. It tells us that a pound sterling (defined as a quantity of silver) in 1209 had the purchasing power of £1.31 in 1250, resulting in an inflation of 0.7 % p.a. on average in that period.
If only it were that simple 
.
In 1266 after Louis IX reformed the French coinage 20 gros tournois (a coin containing just over 4 grams of silver) = 1 livre (“pound”) which then = ~0.18 modern pounds of silver.
In 1180 when Henry II was doing something similar in England, 240 silver pence (the Short Cross penny coins then containing about 1.3 grams of silver) = 1 pound sterling = ~0.69 modern pounds of silver. The original pound sterling in England was based on the now obsolete Tower pound which was closer to 12oz than the modern pound of 16oz. Richard I was pretty much using that same coinage.
So IF we were to use those values:
Richard I = 100,0000 x ~0.69 pounds of silver weight = ~ 69,000 modern pounds of silver.
Louis IX = 400,000 x ~0.18 pounds of silver weight = ~ 72,000 modern pounds of silver.
Which is pretty close to a wash. But there are confounding factors trying to separate actual contemporary values vs just weight of precious metals across a half century.
IIRC, Richard’s brother’s money was close to a wash too.
I read some rather heavy history tome which discussed the complexity of medieval currency, and said, “it’s best to just think of them as coins, and not get too hung up on converting to modern monetary instruments.”
You mean like the gold, silver and copper pieces in Dungeons and Dragons? Yes, that’s probably best.
I remember reading somewhere that the French didn’t pay the full amount anyway. They paid half and the English released Louis with the promise of the other half when he got home. He never paid that other half.
Now that’s lame, as opposed to pulling a “Julius Caesar” so when they ask for 20 talents, get all insulted and insist you are worth 50.