It could be more than just hassle if Thai immigration offices can continue to have have different interpretations of what is required to extend for various long term Visa's like the DTV. For this reason alone I'll be avoiding that randomness by bouncing before 180 days. It's obviously more hassle but I think less risky IMO.
And all you need to show is your original DTV approval PDF or DTV sticker if you used an embassy/consulate. No worrying about whether your original documents you used at an embassy/consulate or on the evisa site will be enough for whichever immigration office you try to extend at.
And a DTV (not the extension) costs? In Taipei or in New Zealand? Read my post again. I was saying that by doing an extension vs. reset by leaving and returning, we are opening ourselves to the inconsistencies of these offices. Those documents we used to get our DTVs may not work to get us our extensions because of these differences. I wasn't commenting about extension prices because nobody knows this.