Elfcrusher, I mostly print mine on self service photo kiosk machine, available in most of supermarkets in my town. I print the files as a standard photo image. The quality of glossy paper is amazing. Cost - 0.30$ for A6(4x6inch). But mostly I design 2 minis on a single template.
1" Metal washers -5$ for a box of 100pcs.
Overall cost of a single mini in my case is 0,15+0,05= 0,2$.