I don't think anyone really released any authoritative research, but back in the early days of Gamergate, when 8chan got ddosed by lizard squad and the database leaked, it was possible to see who spent money to ddos what via some moderately advanced sql queries. And there were a lot of anti-gamers dropping money to target 8chan. A lot of it was $5 to $10, but there were some big whales who dropped a lot. But they were pretty good at hiding themselves. The little ones weren't, but who cares about spending $5 to ddos a site? People want the big fish.