I know there's multiple answers already, but I wanted to add to your info.

Although there are financial calculations you can do to reach that, a laymen approach is to simply work the market price backwards and aim for lowest cost margins possible. Every business and its product in its own distinctive industry (type or focus of service or product) and market (area) is either a price taker or a price makers.
A price taker- market determines just how much a service should cost, typically due to high level of options, simplicity of work, etc. like a non brand tee would go for about $10 typically at any venue.
A price giver- is a highly leveraged firm or product due to beanding or resource capability or due being limited that a product can fetch more. Examples are Nike selling great shoes and leveraging their brand to sell regular screen printed tees for $30ea.

They work the margins backwards, through bulk manufacturing/ordering you can achieve lower fixed and variable costs increasing your yield, all without necessarily increasing your sales price. Once you sell more and your brand or product gains popularity then you raise prices little by little to account a small margins increase in revenue but mainly to help fund the growth with funds for marketing. :)

Hope my piece adds to your tool box! :)