I went through exactly the same discussion in my last job search, and was assured that the offer was in line with industry standards. Even if this tiny company somehow became worth a billion dollars, I’d still make less money than if I’d worked as a senior engineer at Google or wherever. I liked the team and I think it would have been a fun job, but not quite fun enough to work nearly for free. I don’t think I’ll ever work for an early startup as an employee.