Up 47% at the moment. https://finance.yahoo.com/quote/dbx
looks like they mispriced. Most of those gains are accruing to underwriters and speculators rather than the company. Same thing happened to eToys.
its in the company's interest to have IPO investors (their first public mkt investors) rewarded, as it keeps them from selling too much, and it attracts other investors to the stock. dropbox is still unprofitable, so it will probably need to raise more equity in the future, and it helps to reward your early investors
it also makes the investment banks happy -- their clients made money on the deal. if dropbox's banks are happy, that helps dropbox, bc as mentioned above, it will need their services again
the happier public market investors are, the higher the stock price will go. most employees cant sell stock for at least a few months, and if outside public investors are happy, then by the time employees can sell, the stock will be worth much more
if you price too high and all the proceeds accrue to the company rather than investors, you get a debacle like facebooks IPO, where the stocked dropped and didnt recover for over a year