As with everything, you get what you pay for. I can find seahorses here locally for 30.00 ea. Even had an offer of 4 for $100.00 accepted.
The downside is that I don't know exactly what species this horse is, tho I'm pretty sure it's not what it's being sold as. That is no fault of the store owner. Even most seahorse fanatics have to examine a horse very closely to properly identify it. Also, I don't know where these cheap horses are coming from, what they've been exposed to or how they've been kept or handled from one wholesaler to the next. Feeding is another issue. A horse that has not eaten in 3 days may very well starve to death, even when presented with copious amounts of food on the 4th day. It is because they have no stomach and their digestive systems begins to shut down, especially if they are in a weakened state to begin with. And, there is no guarantee how old these cheap horses are. If you get one as an adult, it could be anywhere from 9 months to 7 years old. They really don't grow or change much once they reach adulthood.
The horses that are available from DanU at SeahorseSource and Bruce on Seahorse.org are expensive, but you have to remember that you are not comparing apples to apples, and that shipping is included in the price. Horses from either of these breeders are guaranteed to be healthy, and have never been exposed to worms or disease. Dan's horses have never even seen a bristleworm, as they are kept and raised in bare bottom tanks. They will be shipped to the end owner directly from the farm, with no wholesaler(s) involved, thus they will never be exposed to open systems containing any WC fish. The species will be certain, which greatly helps in raising babies, and the age will be known. You won't shell out 50.00 for a horse that is near the end of it's life. In the rare case that your horse doesn't make it, both Dan and Bruce have return policies. I am not going to name names, but I have had more than one LFS tell me, sorry, it's your loss.
I'm not promoting either Dan or Bruce, I'm just trying to clarify why their horses seem more expensive than those you may find locally. Again, at 150.00 per pair with shipping included, that's still only about 50.00 per horse, which is about the going rate at most LFS.