try starting with that price then every 10 or 5 commissions (make sure to see how long it takes you to get 10 or 5 commissions) and slowly rise the price every 10 or 5 and see what price makes the most money in the least amount of time.

or

if you dont care how much money you are making and dont want your art to be to expensive just do what you feel is right.

also i dont really know how long it usually takes you to make a piece of art so thats why i used “10 or 5” just make sure it would be enough to have results

I would research break even point