I read about this in another thread about knights meeting each other on the battlefield. Apparently they would seek each other out not necessarily to kill each other, but to capture your enemy as a hostage and sell him back for money. So, what happened if this ransom isn't paid? Specifically: Did this happen? Did this (ransoms not being paid) affect even the wealthiest knights, or just petty nobles? I assume ransoms were designed to be payable, so what did it signify if the knight's lord (I assume they were the ones called upon to pay it) failed to pay it? What would happen to the knight?
Hostage negotiations could go on for years, with the prisoners being held in a wide variety of situations, from luxury to pretty miserable (but not usually so miserable they'd die - the captors would lose their money).
The captors might ask for 100,000 livres, the family might counter and say 10,000, the captors might say "Get a loan", and so forth.
If they had accidentally captured someone penniless who claimed they were rich, they might execute them for wasting their time, or if the family absolutely refused to pay. Or they might release the guy on his honor with the promise to pay later. Most ransoms were set at about a year's wages.
Prisoners of War in the Hundred Years War is a great book on the subject. There's a wide variety of experiences when it came to ransoming prisoners.
When King Jean of France was captured in the Hundred Years War his ransom was so large it had to be made in installments (you could say it was a king's ransom!). He was released upon reaching an agreement on the amount but had to leave his son behind in captivity.
A regular knight would probably get similar treatment. It's in the captors interest that you live to pay so some kind of arrangement would probably be made whereby you left a relative in captivity while you went about finding the funds.
If I might hijack the question, how did knights capture other knights anyways, in the middle of a chaotic battle? Did they beat them into submission and tell them to get behind the fighting line and wait for later? Did they handcuff them?
Thank you for the great answers!