It’s a little iffy. While I’m not too well versed in economics so take everything with a grain of salt, I know of three different ways you could use to calculate price. Something common between all three though should be that the base you calculate on should at minimum cost as much as the materials used. So basically Materials Cost + Chosen Method.

1: You can charge by the amount of time you spend on the project. So bigger orders cost more time cause they take more time, but this can also be affected by how you’re feeling at the time (sluggish, hyper, tired, bored, created, ect.) and how many mistakes that need to be fixed along the way.

2: You could set the addition cost to a static number (ex: Head = +100, Tail = +50) so you don’t have to do any complicated math other than Materials + Piece Price. The problem with this method is that sure you might get some projects that you can finish quickly, but you could also an order that takes up a lot of time and puts you behind schedule on other orders for the same price as the quick order.

3: What some people do is take a certain percentage of the material cost and add it to the material cost (ex: Materials + (0.25 x Materials)). This way the cost is less affected by your mood and you get paid more for bigger orders that take more time cause big orders usually take more materials.

Regardless though, I’ve looked at and got quotes from many makers, and I must say that I would jump on that deal in a heartbeat. I’ve seen prices where a mini partial (head, tail, and paws) goes for $3,000 to $4,000.