What you are saying, I think, is it is important to figure out what the expected future value of each of your shares are. All you have to go on, in general, is "what do companies like this one generally sell for"? From that, assuming all the preferred stock get converted back to common stock, you can figure out what each unit of stock is worth. The problem is, the cap table you have now won't be the cap table you have when the company gets bought out.

It's not dilution that is the problem. Dilution is just what happens when you bring in new money. It's that it is very hard to predict what a reasonable upper bound is for the future value of your shares.

Quite frankly, it is one of the big reasons I think trading salary for stock options is a horrible idea. Much better to treat those options are lotto tickets--the odds they pay out in any meaningful life changing way are very small.

Startups don't like to hear this because the truth is, when you work for a startup you almost always take a sizable hit to your salary.