Screen printing lays down one ink colour at a time, through one screen per colour. So the price is driven by how many colours you use, not by how complicated the shape is.
Count the distinct flat colours you can see. A black logo is one colour. A black logo with a red underline is two. Shades of the same colour still count separately - light blue and dark blue are two colours, not one.
The garment colour itself is not an ink. If your design leaves parts of the shirt showing through, that is free.
Smooth gradients and photographic images cannot be reproduced as flat spot colours. We can halftone them, or suggest a different print method. Send the file over and we will tell you what is realistic.
Light inks do not cover a dark fabric on their own, so they need a white underbase printed first. That underbase is an extra screen and counts as an extra colour. A 4 colour design on a black shirt is charged as 5. The configurator works this out for you when you pick a dark garment.
Up to 5 colours per print area. If your design needs more, call us and we will talk through the options.