Most screen printers will have a setup cost, but not all. If someone needs the business, or thinks this work can turned into more work down the road he or she will do the work, and might not charge for setup, screens, color changes or flashing. It doesn't hurt to Ask.
In another thread someone gave an example of a short run for $120 total. If you're talking about 10 t-shirts at $12 each, that's also $120.
DTG screen printers can charge what ever they want as well as screen printers. Not saying they have the market, but no ones holding us to a price. Some printers just don't want to mess with short runs.
Also, heat transfers on Darks, are different then light colors. For one think, most heat transfer printers don't print white ink, so you either have to make the white colors a real light gray, or make it the color of the t-shirt. If you have any circles, you have to cut them out. Some Vinyl cutters can do contour cuts, and do the cutting for you.