The 1209-1914 price and wage database shows that grain prices in the Middle Ages could be very, very volatile. The average price of wheat 1380-89 was 6.5 pence a bushel, 7.2 pence for 1390-99, and 7.8 for 1400-09. However, the peak price for each decade was 9, 12.6 and 12.7 pence a bushel in 1381, 1391, and 1402. There were corresponding years of plenty as well.
At the average wheat price for the 1380s, a Wastel farthing loaf purchased from a baker would have weighed about 18.5 oz, but at the 1402 price only 10 oz, according to the standards set by the Assize of Bread and Ale.
So prices for grain and grain products recorded in particular records in particular years could be very atypical of longer term trends.
Also since bread and ale were such a huge share of the diet of everybody below the gentry, it profoundly sucked to be a landless laborer with a family in a bad year.