Not sure this thread is the best place to get into all this, but in general unless you are one of the very earliest employees of a hugely successful startup you

Not sure this thread is the best place to get into all this, but in general unless you are one of the very earliest employees of a hugely successful startup you aren't really going to get rich on stock. It looks like Thumbtack was founded in 2008. All "early" employees would have joined before 2010. So I feel confident in saying that not joining "some months ago" didn't cost you anything. At the stage the company is at, the difference between the value of your stock grant back then and your stock grant now wouldn't be enough for them to probably care if you asked them to make up the difference as a signing bonus. The difference is likely low five figures at most. A high valuation definitely doesn't necessarily mean a good exit (exits are complicated, read up on participating preference multiples e.g.). And what you should really care about is valuation growth anyway. Anyone can buy an expensive diamond and sell it later at a similar price. Special things happen if you can get your hands on an expensive diamond that nobody else thinks is expensive yet.