Well, I was exaggerating a bit. But realistically, it probably takes about 1/0 the time to make 1 NM, its drop pool, and the items created by its drops (if they're materials) than making an entire dungeon.
I think we got like 20 mid lv NMs when DH and TR were released? Why can't this continue?
For every dungeon they release, give us 5 NMs. That seems pretty feasible.