From what i've seen the rosewill and steelseries 6gv2 seem to be in the lowest pricing bracket for decent mechanical keyboard with nkro. Black widow is also somewhere around this pricing but is 2KRO ....
Higher up the bracket in the 150-190 usd range is the filco/ducky/leopold
And higher up than that in the 200-300 ish range is the Deck Legend and Topre.
And above that is the maximus optimus keyboard
Or alternatively if your looking for cheap; you can check the geekhack marketplace or ebay for a sweet deal on a second hand.