Hmmm, snoopy? No money in forums?
What did it actually sell for?
Or put it this way, what is the highest price any forum has ever sold for? Compare that to sites in other sectors, then consider how it is likely to be for the typical smaller-medium sized forum. It is something that is done largely for enjoyment, not money.
Its nice to compare it to facebook & instagram but that is meaningless, Facebook isn't buying forums, forums aren't doing IPO's. I've never met anyone who has gotten rich from forums, who has?