You're making the mistake of assuming that 100% of the unpaid work performed by a few niche subreddits converts to equivalent wages on the free labour market.
Is anyone going to pay first-world wages for someone to moderate a subreddit? It doesn't seem like anyone is willing to do so, because the mods do it for free. Nobody is willing to pay for this service. Social media companies that do pay for moderators tend to pay them not well at all. It's not a great job. It burns people out. It is in fact entry-level no-experience-needed grunt work.
The caveat was "if the platform really cared". For instance, if I was running a platform that had such an interesting (and important, one might argue) social phenomenon as the Ask Me Anything of celebrities or of vacuum repair techs [1] reaching 22+ million people I would pay the ones doing the work way beyond the equivalent wages of "free labour market". But what do I know, I generally regard exploitation as bad and social media companies as a scourge.
Some moderators have public personas which are valuable to a community, have built up trust, have specific hard to find skills, contribute valuable content, etc. If a moderator (or set of moderators) are able and willing to move a community, the market price of their work is the greater of what Reddit is willing to pay them and how much revenue they can receive from moving their community and capitalizing on it themselves.
Is anyone going to pay first-world wages for someone to moderate a subreddit? It doesn't seem like anyone is willing to do so, because the mods do it for free. Nobody is willing to pay for this service. Social media companies that do pay for moderators tend to pay them not well at all. It's not a great job. It burns people out. It is in fact entry-level no-experience-needed grunt work.
Your calculations are vastly over-inflated.