Why CMYK + RGBO Printing is Standard, Not Extra
Most direct-to-film shops print with four inks and charge more if you want better. We print with eight on every single order, which means the reds come out actually red, and the oranges, greens, and violets that standard CMYK can't reach come out the way your artwork intended. We profile the printers ourselves, in our own shop, on our own film, because color that's close enough is never close enough when a customer is standing in front of you holding the shirt.
Your customers won't know why the print looks better than the last one. They'll just reorder, and that's the point.