Hairstylist here, and own a salon suite. I sell retail products. When it comes to claiming income, do I claim my full retail sales or what I made less the 50% mark-up?

so for instance if my bottle of shampoo is sold for $16 and I paid $8, (50% mark-up) do I claim the full $16 in the income section of do I claim the $8 which is my profit on the sale?