It's a bit more complicated, a lot of factors go into whether or not the AI will give into a demand. First of all, after a demand is made, the AI will never give into any demands from the same player for a number of turns (random number between 20-30 by default), even if the initial demand was too much. AIs with whose opinion of the player is "Unforgivable" or whose approach is "Hostile" will never give in (opinion is the secret number of how much the AI likes the player, approach is the public approach the AI is taking towards the player). If the AI's military might is roughly greater than 85% of the player's military might, they will never give in. If the closest distance between one of the AI's cities and one of the player's cities is deemed to be "far" and the player does not appear to be posturing aggressively around the AI (they don't have a lot of units within "homefront" range of the AI's cities who are not also in "homefront" range of a city the player is at war with), the AI will never give in. If the AI has a Boldness value of 10 or greater, they will never give in.
Otherwise, the AI rolls a dice to determine whether they will give in to a demand. The base chance of them giving in is 100% - (boldness) * 10%. If they have the afraid approach towards the player, the chance increases by +50%, otherwise the chance increases based on the ratio of the player's military strength to the AI's: -10% for 0.85 to 1.14, +10% for 1.15 to 1.65, +20% for 1.65 to 2.49, and +35% for 2.50 and above.
If the random roll's result means that the AI gives in, it will still have a maximum value that it is willing to give up. This value is based on the ratio of the player's military strength to the AI's: 50 for 0.85 to 1.14, 120 for 1.15 to 1.65, and 200 for 1.65 and above. The value of flat gold is the highest between (gold amount) and (gold amount) * 10 / (AI's gold per turn), so 1 gold = 1 point if the AI has more than 9 GPT or less than 1 GPT, but 1 gold = 10 points if the AI has 1 GPT. The value of GPT is a constant (gold amount)*(turns)*4/5. The value of resources is 200 for luxuries and 40*(amount) for strategic resources. The value of Open Borders is 50. Any other item basically has a value of infinity for the purposes of giving into demands.