Wholesale Price = (Materials + Labor + Overhead) × 2
Retail Price = Wholesale Price × 2When you calculate the costs of your materials, you need to consider only the price of what you used to produce one piece, not everything you actually bought. Labor costs are your hourly rate multiplied by the time spent to make one piece. Overhead costs consist of what you need to run your business, such as tools, office supplies, and the like (but not shipping costs).
Note that, in the second formula, you multiply the wholesale price by 2 to determine the retail price. Some sellers may choose a higher number, multiplying the wholesale price by 2.5 or even 3 to determine the retail price (assuming that the market will bear that). The multiplier you choose is really up to you.