If it's a startup, they probably don't want to pay you top dollar. The might just not have it. I wish startup management would be honest about the dollars in investment, And how much they themselves make. I also wish that everyone in a startup got a good size of the pie.
On the good side, if the company grows, you might be in the right spot. Options will likely open up. And, having a successful project on your resume usually helps for the next job.