This is difficult to answer because you haven't given us much to go on. What type of hardware are they building, and how big and fast do they plan to grow?

It really doesn't sound like they have a growth strategy in place yet, so my guess is you would need to create that for them, right? If that is the case, then you would need to show them how you have helped others in similar situations do the same. When I was trying to land a multi-million dollar client, I had to show how I had already helped a similar client do the same thing they were attempting.

If you have that experience, then you can justify by saying, "They paid me X for that service. I know that may be high for your budget (and it should be), but maybe there is a way to work on my salary and also offer something else to compensate for that?"

This gives them a framework to start from, and opens the door to equity conversations. It also puts the ball back in their court, but with a little guidance.

Most importantly though, don't settle if you don't think you will enjoy the job or career. If you know what it will take to keep you engaged and happy, set that as your stop-limit and don't go lower unless the upside potential is worth it.