"Why is gross profit margin relevant here?" I replied to a comment that said Costco has "barely any markup". Markup and gross profit measure exactly the same

"Why is gross profit margin relevant here?" I replied to a comment that said Costco has "barely any markup". Markup and gross profit measure exactly the same thing. If you know one, you can calculate the other. A gross profit margin of 12% means Costco's markup is over 10%. (Or 8% to 9% if you don't count membership fees.) This is low, but it's not nothing.