I go with a variation of colors that's most important to me. The most I'll spend on a Coral is $100. 10 and $15 Frags take much too long grow a respectable size when I'm sitting at the age of 70. I want immediate appearances and satisfaction
If it has good color, It should be in a Hardy state.
If it costs an arm and a leg it isnt worth it.
If the frag or base is dirty, I have to wonder about the care of the tank it came out of.
Things I also consider are how well the base is grown out, Any damage to any part including from cuts during fragging.. consider what many see on some store fragged Acans and Favia. Stores in too big of a hurry to sell a frag are .. iffy in my opinion.. same with home and online sellers. IF you wont make sure you are selling a viable frag, you wont stay in business long anyway. For what is being charged for some of these corals, that is the LEAST they should be doing. For instance, our 2 largest local retailers sellers.. People are taking notice and talking about it..
One other I did not chose is size.. See costs as a basis.. if I am buying an SPS and all I am getting is s non-based out nib.. well I consider that someone not in it for anything but the money.. Not worth my time.
WIth all that said. If I go to a private seller and they tel lme I will cut you a piece off and its up to me to care for it after that, I consider that different.. THing is I am not a high end collector and I know the person I am getting it from..
COnsider that there are going to be very few with the newest and coolest thing.. They make up some name and sell thier first frag to someone who thinks they are getting the latest deal.. Only to find out it grows like a weed and becomes worthless in within a year.. so They change the name and sell it as something new.. I dont trust new.. Its like buying the latest phone only to find out its full of bugs..
Funny thing .. after posting the above, I realize all of those things are relevant A reputable seller should have all of those things checked. Keep in mind.. its buyer beware.....