I have heard of many big sales and I never looked into them.
The biggest high-activity subreddit that was famously "sold" (or monetized from within) is r/SkincareAddiction.
Back in 2015, when the sub had over a million active users, the founder and top mods secretly redirected the entire community's traffic and wiki resources to their own self-monetized blog, using Amazon affiliate links and charging brands hundreds of dollars for product recommendations. Once users found out and provided proof, the Reddit admins intervened, banned the offending mods, and banned their website from the platform.
The biggest high-activity subreddit that was famously "sold" (or monetized from within) is r/SkincareAddiction.
Back in 2015, when the sub had over a million active users, the founder and top mods secretly redirected the entire community's traffic and wiki resources to their own self-monetized blog, using Amazon affiliate links and charging brands hundreds of dollars for product recommendations. Once users found out and provided proof, the Reddit admins intervened, banned the offending mods, and banned their website from the platform.
I don’t know if anything was sold but when Wallstrretbets hit the headlines a few years ago there was a battle to be in charge of the subreddit by 2 groups of mods.
The original group had been lazy and not done anything to the sub in years but when it got really popular they suddenly tried to claim it back from the group that had been building it and putting in the work.
Legitimate mega subreddits are never sold openly, but rather traded secretly via top mod accounts for tens of thousands of dollars before getting totally wiped by Reddit admins.