you're missing something here. When something appreciates, it's MARKET VALUE has increased. I can't just declare it to be more valuable.
A declared value is a requirement for selling additional stock. The new investors are putting in $30M. What does their $30M buy them? 50% of the company, 1% of the company, 99% of the company? Without some valuation for the company it becomes impossible to issue additional stock.
A valuation is part of any offering. If investors buy in then they are getting 15.7% of the company in exchange for $30M in capital. As for the market deciding well that will happen. If the offering is successful then the market (investors buying shares) are agreeing with the valuation, if it isn't then they are indicating the valuation is too high. Either way it adds to price discovery.