You can set your pricing scheme in your tiered prices. To get started, head on over to ⚙ Settings > Tiered pricing.
Click the blue ⚙ Tiers button and select Create Tier:
From here, you can enter a tier name and set whether the price will be found from the RRP (recommended retail price) or as cost plus markup:
You can set this new tier to be your default, meaning all jobs will use this pricing scheme unless overridden.
You can also override the sell price for individual items by replacing the Price directly, or adjusting the Markup and Discount fields: