I’ve just read a good book on the Peasants Revolt by Juliet Barker. The Black Death of the 14th century immensely reduced the work force. But England saw a huge economic upswing and labourers saw their wages shoot up, and landlords tried to poach labour from each other by offering freedom to serfs in return for paying cash rents. Unsurprisingly free labour was much more productive than serf labour. Nor was it bad news for landlords, as there were fewer of them with bigger estates than before, and many of them switched to sheep-farming, which proved very lucrative. By 1400, England’s GDP was probably the same as in 1350, but with half the population.
The Revolt was a good example of De Tocqueville’s view that revolutions occur when things are getting better. Most rebels weren’t poor, but rather well off peasants, burgesses, blacksmiths, innkeepers etc. even some minor gentry, and MP’s, who were increasingly literate, could afford to go to law against grasping abbots and landlords, and who were protesting over unjust taxation and corrupt government (eg you had magistrates charged with enforcing maximum wage laws cheerfully breaking them with their labour forces, landlords imposing feudal fines much more rigorously on prospering peasants).
It’s also worth noting inflation can happen in weird ways. This meant both that farm labour was more valuable, increasing wages, and food scarcer, increasing food prices. However, the cost of things like swords declined. Because so many people had died, there were a lot of weapons and suchlike that belonged to the recently departed. Inflation, therefore, was affected in opposite directions for different things but caused by the same plague.
Historically, silver and gold were used to determine value, that value varying in practical (though not nominal) terms according to the percentage of precious metal used. Nowadays, coins have very little inherent value (with rare exceptions, such as gold sovereigns).
Which does raise an interesting point. The actual coins you have are worth almost nothing. But because society all agrees to pretend they have value, they do.