They win money do that helps with the cost
there are many different situations. many pro riders come from wealthy families (remember though, not all)! as they get a name for themselves in the equine world, sponsors come and support these well performing riders, and through this they get free tack/apparel to support that end. catch rides are great too, as they get to show these horses free of show fees. people pay for famous riders to show their horses.
Sponsors and syndicates for purchasing horses. Some of them come from horsey families or families that have money, but a few don’t. Eric Lamaze and Kent Farrington are 2 that didn’t come from money or horsey families.
Compete in money classes and work hard
Also they where probably born with money to begin with 🤷🏼♀️ But not all the time