Quoted from JY64:A %100 mark up at any retail establishment is standard
You are so far away from reality. You think a car dealership gets their cars from the manufacturer for $20k and sells them for $40k as well?
A 100% markup may apply to some smaller, low-cost retail items - clothes, shoes, etc. But there are many, many items that are around +/-10%: video games, consoles, legos, cars, machinery, etc etc.