Most items, like clothing, toys and such are keystoned. That means if you buy it for 10 bucks , you sell for 20. Some add a percentage or so over that to allow for markdowns, and items that are sold for less than keystone.
Jewelry and cosmetics is about 500%. Say they buy a cream for 20 bucks, they sell for 100.
IDK about electronics.
I know jewelry has such a high mark up because it is always on sale. That allows for those 30, 40 and 50% sales!