DTG is a whole new world in itself, with limitless possibilities to print on different fabrics of each and every color (including dark garments).
The are multiple DTG machines in the market with Epson and Ricoh industrial print heads.
Any DTG on a light color will cost around 30Rs - 60 Rs in India (A4 size). And can be 4 times on a dark garment.
Comparing to Screen Printing, It's Costly can't say specifically about the cost without the design's but It's like 10 to 20 times costly than traditional screen printing. If you're looking for cheap Tees with a simpler design, bother not with DTG but if the design is too complex go for it though the cost will be ridiculously high ....But in screen printing, you're limited by color whereas in aDTG by imagination. Good Luck