Often times the price is determined by the presale price given to VC. The price should not dump below that price or else VC would be selling at a loss.
While it is true as you imply that Venture Capitalist (VC) tend to sell their tokens below the presale price, this is not always the case. They may have a variety of reasons to sell their tokens, including diversifying their portfolio or taking profits. Additionally, some VC may have lock-up periods or other restrictions that prevent them from selling tokens immediately after launch. Normally the price at the time the token is launched, factors like market demand, utility, and overall market sentiment play an important role I think.