It's called a "secondary"[1] and it's extremely common. It's how both investors and founders make millions on startups long before an acquisition or IPO, often before the startups are profitable.

As for my take on VCs in general, of course I don't have any actual data to support my rant, it's purely anecdotal based of my personal experiences and should be treated as such.

[1] https://en.m.wikipedia.org/wiki/Private-equity_secondary_mar...