I am old enough to remember when you could buy seahorses in the mail. The advertisements were in the magazines, Fish and Game, Hunting and Outdoors Man. My dad was an avid trout fisherman and he got all the fishing magazines. Of course I would look through them and saw the small ads for pet seahorses in the very back of the magazine. The ads would have a small drawing of a seahorse and maybe a fish tank. You could buy a pregnant "papa" seahorse that was guaranteed to give birth to dozens of baby seahorses.
What those ads didn't tell you was the fact that those seahorses were caught wild off the shore of Florida and that seahorses are a difficult salt water fish to keep. The seahorses were also the dwarf variety and not the larger seahorse that people were more familiar with.
Since then I have seen the larger seahorses in pet store close to me and with their sale price tag of $40 and up, I think I'll pass on that pet. Occasionally I do see the dwarf variety seahorse in our local pet store and they are more reasonably priced but I would suggest to anyone interested in acquiring one that they read about them first.
One of the hardest aspect of keeping dwarf seahorses is feeding them. They require freshly hatched baby brine shrimp. You not only have to worry about raising the seahorses but raising their food too. That alone is much too much involvement for the average fish owner.
If you are up to the challenge, keeping a dwarf seahorse might be an ideal pet for you.