Bulk DTG Print Pricing - Shirt Colour Change

When I make an invoice for DTG printing but want several colours of tees, the price resets and charges it as a seperate print run. 

Normally we would keep the pricing the same and give them bulk pricing since it doesnt matter what colour tee they choose, its all the same on digital (besides white being a bit cheaper)

There should be a feature or workaround for clients who want bulk multi coloured tshirt printing with the same design.