Are your questions meant to be a brainstorming on how an ideal site compensates Moderators or something else? A site like Reddit is depended on users visiting and generating content (discussions). Moderators are just middlemen that facilitate those discussions. a site like Reddit probably doesn't value the idea of moderators very much because anyone can become a moderator. Moderators aren't influencers, so they don't move communities. The value of a community are of the people that participate in that space and the biggest draw of reddit is that its easy to participate in multiple communities at the same time.

$3.4m of work divided by how many moderators = probably insulting to pay them would be my guess. Sure, the work and value isn't equally distributed.

Send thank you cards, annual gifts, maybe some sort of exclusive-ish discount program (a lot of corporations get employee discounts to large advertisers, maybe you could extend that to moderators at some minimum level of effort)

Maybe some token stock grants, if you can find a way to make that not a giant hassle.