The Most Expensive Horse Breed In The World
First things first: Pretty much every breed of horse is expensive. Even free horses are expensive because the average free horse still eats 15 to 20 pounds of hay a day and has to be regularly wormed, shod, and vaccinated — and we won't even get into the part where eventually he or she will get equine colic and the vet will have to come out twice and you'll end up spending $500 for some mineral oil and a bucket of water, but whatever. Horses are expensive.
As far as what you'll actually spend on simply obtaining the horse itself, though, that varies a lot depending on the horse's breed. You can adopt a wild mustang for around $25, but you know, it's a wild mustang so it's not like you can just climb aboard and go, unless you especially want to become a rodeo cowboy. Cheap horses almost always require professional training, so you're not really spending just $25 on that mustang, you're spending $25 plus another $500 a month for your trainer. They do make pretty lawn ornaments, though.
In the upper ranges, well, it's kind of hard to say what the most expensive breed is, because you can almost always buy inexpensive horses even in breeds with high average sticker prices, and what you end up paying depends a lot on the animal's parentage, conformation, training, and history. Some sources say Arabian horses are among the most expensive, but unless you want a show-quality animal, the typical sticker price of an Arabian is actually pretty average.
The Akhal-Teke's the most expensive horse, of course, of course
If you're going to talk about the breed with the highest number of ridiculously overpriced individuals, then hands-down you'd be talking about thoroughbreds. According to the LA Times, in 2000 a thoroughbred racehorse and Kentucky Derby winner named Fusaichi Pegasus sold for an undisclosed amount, rumored to be on the order of $70 million. Although we don't know the exact figure, we do know that Fusaichi Pegasus broke the previous record of $40 million, set by Irish Derby winner Shareef Dancer in 1983. But not all thoroughbreds have those kinds of price-tags — derby winners have stud potential, so that big investment pays dividends. But you can actually get free thoroughbreds, too, usually in the form of ex-racehorses who never won anything but are too crazy for normal humans to ride.
If you're talking about consistently expensive horses (few free versions available), the Akhal-Teke is one of the most-, if not the most-expensive horse breed in the world. There are a couple of reasons why this breed is out of reach for the average horse enthusiast. First, there are only 8,000 of these animals in the whole world, which makes it a rare breed. Second, Akhal-Tekes are carefully bred for endurance and performance, which means they make great horses for seriously competitive equestrians. And the Akhal-Teke is also one of the oldest breeds in the world. The starting price for an Akhal-Teke is $100,000, which is basically a down payment on a decent home in California.