No offense, but you don't understand. Opportunity cost means specifically you aren't leaving money on the table. It means you are grabbing the pennies when you could be pursuing a more lucrative options. When you are 20 those options don't mean a million dollar deal, they mean not taking the better job that pays about the same but lets you earn 20k more in 2-3 years because you are doing something you love and thriving in it with fewer restarts. That over 20-40 years adds up to "millions in the bank", which is what the original poster said, not millions on the table.
A few times not seeing bad management in a startup where you took options rather than a decent wage would do it too.