I've seen them in the vicinity of $15-20. Expensive for a freshwater fish, but not bad overall IMO.
The problem is finding them. I've only seen them in one place (Fishnook in Acton MA) and even there, I've only seen them there 2 or 3 times over the last 2 years.
Mine was quite small when I got him (maybe an inch?).
I've had him (Her?) for about a year and a half now. He's about 4.5 inches maybe a bit over now. As I read, In the wild, they will grow to a tad over 8 inches, but one kept raised in captivity will be lucky to see 6 inches.
These are a mediumly aggressive fish. They will hold their own against other likewise fish, eat anything that will fit in their mouth which is huge. He actually opens the wide mouth so wide so quick, prey is 'vaccumed' in. Rule of thumb is they could eat fish 1/3rd their size, which means no fish under 2" in the aquarium.
As long as you don't house them with any particularly shy or aggressive fish, you should be good. Also should note that include's gourami and betta's, they are all cousins, and don't get along together.
The Leopard Ctenopoma has a lot of personality, and IMO is the smartest in my tank (which would make sense as he is the most advanced predator in the tank and [common biological theme] the more advanced the predator, the more brain-power/wit they need.)
I love his camouflage pattern, especially how he evolved that large black dot next to his tale that immitates an eye. So to many other fish, they can't tell if he is coming or going. Devious.
I like to tell people, even when you don't see the Ctenopoma in the tank, he sees you, and is watching you. People scan over the tank very carefully until they see an eye poking out watching them from behind a bunch of plants.
For a good size fish, I'm amazed how easily he can disappear if he wants to.
I keep an anubia on a good sized piece of wood in my aquarium and that is the Leopard Ctenopoma's favorite spot to hang.