Blockers
Because Knights can make runes like mages and Paladins, they use their high defense skills to gain money and help low levels or mages and paladins to kill strong monsters such as Giant Spiders or Dragons
The prices are based on the Blocker(the person), the Monster, the time or amount of monsters.
Maybe you can Provide 'em the UH's and get a lower Price.
Good Luck ;)