At the bare minimum, wouldn't you have deserved whatever the discrepancy was between the below-market salary they offered you and the market salaries you could have gotten elsewhere, aggregated over the years you were at the startup? I'm guessing that would be more than $8k in total.
You also had to deal with the post-acquisition career turmoil of either losing your job or having to work for the acquiring company, neither of which would have happened had you taken a market salary at a larger company.
I wish. I took the position because my previous position was so terrible that I was taking the first offer someone shot my way. Had I not been so desperate and naive I may have negotiated for more salary or equity. I did manage a 43% raise post acquisition (still below market). I wish I would have put the whole 8k into the Tesla IPO too but I can't go back in time.
You also had to deal with the post-acquisition career turmoil of either losing your job or having to work for the acquiring company, neither of which would have happened had you taken a market salary at a larger company.