Meh. The catas are upper (at least semi-)feudal nobility right ? That means they have big-ass estates (presumably largely or entirely tax-exempt) to furnish the revenues for the expensive harness, the at least as expensive horse harness, a trained warhorse of high enough quality to carry the whole shebang, and the free time required to practice combat with all that. Plus of course all the other odds and ends feudal landholders need to take care of (starting with armed retainers, guards, other household staff...), not to forget their nigh-universal tendency to be varying degrees of pains in the ass for their monarchs...

Kinda the same thing as late-period Medieval European knights basically. Small wonder they cost like the dickies and don't exactly grow in trees - and cannot be used in great numbers.