Was early modern writing paper expensive? (2018) - https://news.ycombinator.com/item?id=20559968 - July 2019 (4 comments)
https://youtube.com/watch?v=-XoTGFC-0NA&pp=ygUrQ29ubmVjdGlvb...
For the average person paper would indeed have been expensive but for those who had disposable income and a reason to use paper it would have felt less so.
But it was certainly more expensive than it is now that 500 sheets of A4 at Tesco cost less than 5 GBP and that is one part in 6 400 of UK median annual household income.
https://www.folger.edu/blogs/collation/writing-paper-expensi... says that the going rate for a quire of ordinary paper was about 4d.
Even in 1800 annual income for most people was under 20 pounds. So 500 sheets would cost one part in 60 of annual income (20 pounds * 240 pennies per pound/(4d per quire * 20 quires in 500)). That's about a hundred times more expensive in purchasing power terms. Presumably the further back you go the higher the price and the lower the income.
But the poor didn't write so the comparison is far from exact. For the wealthy it would still have been more expensive than now but not importantly so.
See page 10, Figure 5: Price of paper/CPI in England, 1356-1869, and the Netherlands, 1450-1800.
This shows that the price of paper declined exponentially from 1350 to 1650. The decrease in the cost of paper made printing economical. Printing on vellum was not. They point out that each Gutenberg Bible printed on vellum required the skins of 300 sheep.