I don't think the cash reward is the thing to go. As people duely mention, the top 15 scorers aren't necessary the top 15 pilots, nor pilots which would deserve such respect or rewards. While a lot of them are good people both in skill and attitude, whom I would wish to learn flying from, others are bitc*y whiners who can never stand a death from "unknown" pilots, known to dump trash at ch1, would harass other people, and will sell his soul for points and scores if necessary.
Cash reward will just bring cynicism and disapproval from the real pilots who don't do the chest-thumping bit, or low in general scores due to limited flying time. The sneers and contempt against the "score-potatos high" aspect of AH will worsen AH MA environment which is already trashy enough.
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Instead, give them some other type of reward. A non-profitable, honorary thing should be fine enough. Maybe something like a special squadron marking (in concpet something like the sort VVS Elite Guards received) approved only by HTC, or a special icon visile to friendlies.. something like maybe a star next to their names, making them recognizable as pilots with great skill who is officialy noted by HTC as winners of the shoot-out contests... or maybe a special(!) rudder colors/markings such as early LW pilots dabbled in.. or maybe a special text like "System: PilotX, an HTC Elite, has landed with X kills"..
This is reward enough to satisfy personal egos, and yet not big enough to cause scorn and open contempt from those who do not approve.