Anytime stock changes hands in exchange for money it's reasonable to use that transaction to value the company. It doesn't matter if it's the company selling a

Anytime stock changes hands in exchange for money it's reasonable to use that transaction to value the company. It doesn't matter if it's the company selling a piece of itself or employees selling stock to an investor. Someone is still paying money for ownership. If anything, employees selling shares probably makes it easier because it's common instead of preferred shares being sold.