Place your regular rates in column "A" and enter the formula "=90%*A2" -- without the quotation marks -- into column "B" to calculate the final value of the rate with a 10 percent discount.

Looking at key cards, Perez’s 2020 Topps Chrome Formula 1 Refractor PSA 10 is down 55% over the last 365 days and is now trending below $50. This card traded at or above $100 a handful of times ...