Dropbox will price IPO at $21 per share

If you mean that the title should describe market cap rather than share price, this does occur sometimes and I agree that it can be a more useful metric. The share price needs to be mentioned as well, though, as it's the actionable term (to invest $210k, you buy 10,000 shares).

If you have a $20 billion company and sell half of it in the form of 10 billion shares for $1/share, it's not really any different than selling it in the form of 100 million shares for $100/share. The same amount of money will buy the same amount of the company. And since price changes are often given in percent change, it doesn't matter if you buy 100 shares at $1 or 1 share at $100. If the stock doubles, you'll have $200 either way.