It seems like something people would be massively opposed to, but for the most part everyone seems to have felt it was for a worthy cause.

They had actually just experienced a similar tax a few years earlier, the “Saladin Tithe”, which was collected by Richard’s father Henry II to help pay for a crusade against Saladin (who had captured Jerusalem in 1187). As the name suggests, it was a tax on 10% of all income and propery, and it was collected per parish. The parish priest and local Templars and Hospitallers were responsible for collecting the money, and they probably raised about 70,000 pounds. In this case, churches seemed to think they were unfairly targeted - why was it collected by parish rather than by shire? But the general feeling was that recovering Jerusalem was a good idea so everyone wanted to contribute as much as they could.

The crusade helped the Kingdom of Jerusalem recover some of its territory, but not Jerusalem itself. Richard also came into conflict with the king of France (Philip II) and the Duke of Austria (Leopold V), and after they went home, the new king of Jerusalem, Conrad of Montferrat, ended up being assassinated. Conrad was related to Leopold as well as the Holy Roman Emperor Henry VI, so in the Empire it was suspected that Richard was behind the assassination. On his way home in 1192, he was taken prisoner by Leopold, and Leopold and Henry set his ransom at 150,000 pounds.

The money was never referred to as a “ransom” - it was described as a dowry for Richard’s niece Eleanor of Brittany, who was supposed to marry Leopold (although they never married). Richard’s mother Eleanor of Aquitaine began collecting the money from England, and from Richard’s lands in France. She imposed

“…a 25 per cent tax on income and on the value of moveable property, and [appropriated] the year’s wool crop from the Cistercian monasteries as well as gold and silver plate from churches throughout the country.” (Gillingham, Richard I, pg. 239)

Imperial representatives came to England to make sure the silver was pure and would be transported safely. It’s actually hard to know exactly what was taxed, and where exactly all the money came from. Financial records from medieval England are usually extremely detailed, but the Exchequer kept separate accounts for the collection of ransom money, and unfortunately none of them survive.

Apparently this time the population of England didn’t consider it an excessive burden, even though it was twice as much money as the Saladin Tithe. Just as the crusade was a good cause, ransoming the king was a worthy cause as well. The medieval chroniclers who mention it often talk about the “common consent” and “infinite generosity” of the population - of course they may be trying to justify the tax in hindsight, but it’s probably an accurate assessment, since the ransom was collected quickly with no major opposition.

Some people were actually in favour of it because it was mostly collected from the church. The wealth of the church would be an even bigger issue in the 13th and 14th centuries, but even as early as the 12th century there were complaints about how much wealth the church appeared to be hoarding. Surely they could afford to give a little extra in times like this!

Aside from the church, not everyone was happy, and some people also questioned the extra cost of the triumphal procession held for Richard when he returned to London. It’s also likely that Richard’s government was chronically short of money and he couldn’t effectively wage war against Philip II, who had been invading his lands in France while he was gone. Richard spent the rest of his reign fighting Philip and he was killed in battle in France in 1199. His brother John lost Normandy and many other English territories in France, starting only a few years later in 1204. Richard and John had to raise even more taxes to pay for this war. If there was never a ransom, there probably would have been more money available to fight Philip? But

“Despite the extraordinarily high cost they had to pay, Richard’s subjects appear to have been glad to see him back” (Gillingham, "Coeur de Lion in captivity", pg. 74)

The population’s willingness to pay is sometimes even cited as the origin of the idea that taxes were paid by consent, that the government had responsibilities towards taxpayers, and that no one should be exempt - sounds familiar from American colonial history! It may be a stretch to say that these ideas originated almost 600 years earlier, but J.R. Madicott argued

“It is highly probable…that the association between national taxation and general consent established in the granting of the Saladin Tithe was confirmed by the levy for Richard’s ransom.” (Madicott, pg. 120)

So, both the Saladin Tithe and Richard’s ransom faced some minor opposition, but it looks like people were willing to pay for both, no matter how much they may have grumbled about it in private.

For some relating reading, see these previous questions:

How was Richard the Lionheart captured? Where was his army? What did his captivity look like? by me

Richard I of England paid a huge ransom to the Holy Roman Emperor, how did that impact the HRE? by u/Coeurdelionne

Sources:

John Gillingham, “Coeur de Lion in captivity”, in Quaestiones Medii Aevi Novae 18 (2013), pp 59-84

John Gillingham, Richard I (Yale University Press, 1999)

J.R. Maddicott, The Origins of the English Parliament, 924-1327 (Oxford University Press, 2010)

Christopher Tyerman, England and the Crusades, 1095-1588 (University of Chicago Press, 1988)