6 billion seems REAL high
But reddit, like twitter, has demonstrated it is a brand/service (just service in the case of xitter) that people are addicted to and will not quit. And stuff like AMAs and astroturfing demonstrate it has a lot of marketability.
Combine that with it being a treasure trove for LLM training and I could easily see it pulling 2-4 billion. More if the FOMO model works out for them and they have /r/wallstreetbets do another "the greatest act of democracy in all of human history" or whatever the tagline for rich people to convince idiots to help them manipulate stock prices.
So it would be less about buying a product to keep for a long time and more about something to exploit for a few years and throw it away.