The stock that the VC owns and the stock that the employee owns are materially different and thus have different values. The kind of stock the employee has is not for sale.

It is better for employees if the stock they own (or have options for) is initially low-priced (for tax reasons).

This whole "valuation set by auditing" is kind of meaningless -- it's as artificially low as some might think the VC valuation is high. It's based more on regulations about what is valuable than what the market thinks is valuable. For example, cash in the bank, factory equipment, and accounts receivable are worth something -- having a billion free users is not.