What breed was the most expensive horse sold?

It's difficult to pinpoint the most expensive horse ever sold definitively. Here's why:

* Different types of sales: There are sales of racehorses, show horses, breeding stock, and even horses for everyday use. Prices vary significantly depending on the purpose and pedigree.

* Private transactions: Many high-priced horse sales are private and not publicly announced.

* Value fluctuations: The market for horses can be volatile. A horse might be sold for a high price one year, but its value could change drastically over time.

That said, here are some noteworthy examples of expensive horse sales:

* "Fusaichi Pegasus": This thoroughbred racehorse sold for $70 million in 2000, making it the highest price ever paid for a yearling at the time.

* "The Green Monkey": Another thoroughbred racehorse, sold for $16 million in 2006, making it the most expensive yearling ever sold at auction.

* "Sea The Stars": This thoroughbred racehorse was bought for $40 million in 2010, and its stud fees have since generated significant revenue.

* "Frankel": Another famous thoroughbred, Frankel, sold for an estimated $200 million in 2013 when he retired to stud. This value is based on his potential earnings as a sire.

It's important to remember that these are just a few examples. There are likely other horses that have sold for significant sums, but the details are not public knowledge.