There is a huge risk in opportunity cost to join a startup.

Some founders such as serial entrepreneurs who have proven their value, I could see 100-1000x. However, first-time and inexperienced founders should not get more than 10x their employees given that they providing a lower expectation.

Also priced into it should be the difficulty for you to do it yourself. If the company truly does amplify your value by 1000x, then by all means it is a fantastic deal.