Printing cost = $0.25 + $0.7 + $0.15 = $1.1
Ink cost: Here we assume the graphic printing size to be A4 letter size. Generally speaking, an 1000ml ink valued $100 can support 400 prints in average. That’s to say, in this case each print cost 2.5ml ink valued $0.25.
Film cost: Here we assume the printer to be a sheet-fed version. 100 pieces of printing film cost $70, equivalent to $0.7 per sheet. 
Powder cost: An A4 letter size print normally requires 1.5g adhesive powder. 1000g powder cost $100, that’s to say the powder cost of each print will be $0.15

Equipment cost = $1.15 + $0.25 = $1.4
Product purchase: Conservatively estimated, an A4 DTF printer, plus an oven and a heat press, all together cost about $3,000. 
Product cost can be greatly affected by machine lifespan and one's printing plan. Assume all the machines work in good condition for a year, that would be 52 weeks in total. Meanwhile, assume that we print about 50 t-shirts (an A4 letter sized print on each) a week. That’s to say, the product cost of each shirt equals to $1.15=$3,000/52 weeks/50 t-shirts.
Maintenance cost: We previously assume that all the machines would support a year of smooth performance, yet this ideal situation can only occur when there’s regular maintenance performed, especially for a digital printer. Considering the possibility of clogged or damaged printhead, we now suppose a printer needs printhead replacement twice a year, and each costs $320. Therefore, the maintenance cost of each shirt equals to $0.25=$640/52 weeks/50 t-shirts.

Fabric cost = $3
Here we take T-shirt as example. T-shirt price varies greatly from the fabric substrate and design. On Alibaba wholesale websites, a shirt that meets quality requirements costs around $3.

Other cost: 20%
This cost includes expense caused by printing waste, human labor and power, etc. Here we add a 20% cost rate for them to further calculate our total printing cost.