That koi was, I believe, Sakai's top nisai showa during the April auction. It was bidded up to 6.5m yen. It had incredible body and pattern, but looked relatively finished for a nisai. Unfortunately I did not save the photo in my computer, so I can't post it up here. Very few Sakai nisai sell for this amount, even if they are good show quality fish, so don't take this extremity as the norm. Auctions tend to distort values somewhat.
It's really difficult to generalize how much a show quality fish from Sakai would cost. Fish that are good enough to win show prizes at a small size may not have a brilliant future as they are more or less already finished (and are in most cases male), so are usually much less expensive as one which looks currently "crappy" but is a fish with a huge future potential (ie a true blue tategoi). Indeed, many GCs almost never win anything during their younger days. It really depends on what you want...a current show fish or a "tategoi" (used loosely) with show
potential.