What did a medieval court jester earn?
4½ pennies a day at court, plus a yearly gift and free ale.
About $1,300 a month in today's gold.
A month of that pay weighs about as much as 10 paperclips in gold.
Jokes non-refundable. One fool held 30 acres of land for a yearly leap, whistle and fart before the king.

Where the money came from
The word jester came into use only in the 1500s, from the older gestour, a storyteller or minstrel, and lords kept some minstrels as jesters. Roland the Farter held a manor in Suffolk and 30 acres from Henry II for a jump, a whistle and a fart before the court every Christmas. In 1303 the future Edward II went swimming with his fool Robert Bufford and had to pay him compensation over a trick in the water. Edward IV's household book of 1478 set out what his minstrels earned: 4½ pence a day, but only while they were at court for the five great feasts of the year, and they had to leave the day after. On top came a yearly reward, and clothes for winter and summer or 20 shillings each instead. Every evening they shared 4 gallons of ale; in winter they had wax candles and firewood, and lodging near the court for themselves and their horses. A sick minstrel got two loaves, a dish of meat and a gallon of ale. They had no share of the rewards given to the household, and the king would not have them asking his lords for rewards. In the 1470s a master mason earned 6 pence a day and his skilled helper 4, so a minstrel at court earned a little more than the helper and three quarters of the master's rate.
Sources: en.wikipedia.org · en.wikipedia.org 2 · en.wikipedia.org 3 · edwardthesecond.blogspot.com · abrahamadcock.com · mpra.ub.uni-muenchen.de
What a court jester's pay bought in 1350
a gallon of ale: less than a day's pay
a plough: 5 days' pay
a fur-lined garment: 3 weeks' pay
a year at Oxford: 20 months' pay, more than a whole year of it
a craftsman's townhouse: 2 years' pay, more than a whole year of it
Every price of 1350, with its source, is on the prices page.