The main cost is in the colour screen setup. So less colours will make your prints cheaper and higher quanities will reduce the unit price per print. 

With each colour layer you can choose between a 'Smooth'  (emulates artwork textures) or 'Halftone' (converts midtones into a dot pattern) finish.

Lighter/inkless areas & clear borders are essential in preventing smudging,  drag marks and ink pooling.

140gsm paper offers the best finish; heavier options cost more and are less suited to the print process.

Ensure the colours of your submitted artwork match your desired outcome as closely as possible

It's the nature of the best to have some misalignment throughout your print run, making each print unique.