Actually--
these fish are protected and its illegal to collect them.
Thats said, captive bred offspring occasionally pop up.
last yr on a japanese website, there were a few leafy seadragon babies for sale. they were captive bred offspring. IIRC they were ~5grand USD/ea
Also remember these are temperate water fish so they require cold water, and they only eat live shrimp.
I was speaking to a curator of a public aquarium a few years back, and she mentioned that it cost more than her yearly salary to pay for the live shrimp their leafy exhibit ate.
gotta have deep pockets for these fish