I am near Denver too. They are cheaper here, but there are more of them and most don't want to ship them to get the extra money and the local market is saturated a bit and everybody who wants one has one already. If you want a LEGIT 6" inflated one shipped (not 4 inches), then look to spend at least $1000, if not more. At 6", they are ready to be cut again and the seller can get two of them, so this size is harder to find for sale. Like any coral, local marketplaces can have cheaper, or more expensive prices, and you might get lucky and get somebody to ship one. When looking, I would only use prices that have shipping since these are more indicative of the market... and size.
True yellow tips and marbled foot are the tell-tale signs. Lineage back to Keys Island in Denver, which is not in business anymore.
Beware of imposters and photoshop. The real-deal needs no trick lighting or doctored photographs. Some of the cheap ones that you are looking at might be non-legit. Pics under only blue light should be avoided, IMO. If they won't show you the marbled foot and the tips are not yellow, then walk away, IMO. One good thing about Denver is that they are usually legit pieces since they were local.
I have been keeping these since they blew up and got some of the first ones that I could. If you have any questions about care, then let me know. They are not hard to keep, but they do need to be the only BTA in your tank - while a few have kept them in with other BTAs, this is rare, most that have tried have them slowly shrivel up and die. They do wander around a bit. They do well in a variety of tank conditions and will accept nearly any light type with medium intensity, or higher. Also, 6 inches in some tanks might be 4 in yours, for a while. They don't often split - nearly all of the clones that you will encounter are cut, but this is no big deal and I would buy either. I did have one split naturally a while back and I was shocked since this rarely happens, at least for me and my friends that keep them. You just have to make sure that they are healed fully before shipping from either a cut or a split. I wait for them to grow again and have the mouth dead-center.
I would not worry about looks too much if the rest matches up. These are the same clones in the same basket in the same tank... one has the strong bubble tips and one does not. Both of these are well more than 6".
