This class of titleless landholders would be comparable to the burghers of medieval Europe and were held in just as much disdain by commoner and noble alike. They, individually, tended to be richer than most minor lords and yet chafed from not possessing the privileges and rights nobles enjoyed, frustrated that their raw monetary power didn't translate automatically into real power and influence. More than once and in more than one kingdom, these plutocrats had tried to simply buy their way into nobility and thus into the realms of hard power, often using it to the benefit of their cronies. It never really ended well for those realms that let them get away with this, hence the constant suspicion and fractious relationship between the aristocratic and the oligarchic powers in society.