You guys are correct. Both Weedy and Leafy Seadragons are HIGHLY protected species. There is only ONE permit issued at this point in time to take them out of the wild. The collector is VERY limited - and for very good reasons. This animals are VERY rare. To add to it, they are VERY hard to keep. A handful of aquariums keep them, and only two places have had any luck breeding the Leafy. Weedy are a little easier to deal with, but not much.
Cost for most zoos/aquariums will run between $10,000-20,000 USD (depending on age of the animal and how long it's been in captivity).
Dallas World Aq has the largest collection of captive Leafies. I highly reccomend going to check them out.