To be honest, I'm not entirely sure this will work 100%. If only because there are people that have proven through action that they're willing to spend $100 to make a single joke that lasts but a fleeting moment for several thousand people.
As in, those TF2 wedding rings. There were people there using those to make Anne Frank jokes, and that cost just the same amount. Add the fact that the joke may well go out to a larger audience, for a slightly longer time, AND the dollars go to charity, and you'll most likely have at least those people, and possibly a few more, happy to make those jokes once again for the same cost.
Granted, this is still a good tactic to drop off 99% of the trolls, and indeed those few jokes will be somewhat funnier due to a lack of over-saturation. So... Well played, I suppose.