https://marketplace.tf/items/tf2/199;15;u702;w1;pk236

March 22, 2019 sold for $55.00 - Buy order

March 22, 2019 sold for $119.95 / 1.80 = 67 keys

April 10, 2019 sold for $85.00 / 1.77 = 48 keys

May 12, 2019 sold for $94.95 / 1.80 = 53 keys

May 25, 2019 sold for $119.99 / 1.82 = 66 keys

I cannot find an item history for this item, so I am unable to determine if the second March 22nd sale to April 10th sale is an outlier, so I am going with a range that covers all these sales.