I keep almost all my morays chilled (and would make that all of them but don't want to spend that much money on a 'like to have'). Some of the super tropical species might need to be kept in the upper 70's/low 80's, but none of my Japanese morays seem to care being kept at 68 degrees (the deep water species and neglectus need cooler temperatures as well). Besides the cost I love chillers though.
In terms of keeping anatina in warmer water - I honestly don't know. I've spoken with exactly no one else that's ever kept them. My supplier works with Aquariums all over the world as well as European wholesalers and he's never collected them, seen them offered or heard of them being kept either. Some subtropical fish, particularly ones that live close to shore can be kept in warmer water, others can't. My advice would always be to keep them cool.
The price tag seems to be the nature of the business. My two anatina were much more expensive than I'm asking for here, mainly because the supplier isn't used to selling two fish at a time. He cut me a deal this time, but shipping from Europe kills me, and right now the dollar is getting bent over by the Euro, so I get my but kicked on exchange as well.
As far as the Japanese species go - Dragons can be had for $600-700 because they sell lots of them. Kidakos too, but they tend to come in smaller which saves on shipping. The others, I just think they sell so few of them that the few buyers out there are willing to spend four figures on them - though I do remember the Koke you're talking about, which I think was 7-800 bucks. At any rate, I can let you know next time a Koke pops up if you want.