The short answer to this is - how long is a piece of string? Obviously costs change depending on the size and level of detail, so we tend to do what most people do, and charge for our time. Full colour, detailed pieces also tend to take longer than greyscale ones.
We have a flat hourly rate and the shop also has a minimum charge. Contact us and we'll do our best to give you a ballpark figure, or we'll set up a consult for you so that we can give you a more definitive idea.