Senior iPhone dev's are commanding $120-140k. Many only have 3 years experience on the platform. For some it is their first platform. That's close to the top of the industry pay.
You won't fit in.
If so I would suspect some serious arrogance and ego on the part of the company. Most of the start-ups that I have been part of have viewed older members with reverence for their experiences.
90% of your experience will just be in the way of what needs to get done.
This is illogical, 90% of what we do is reinvent the wheel in the next platform, we are currently reinventing the mainframe-> desktop -> web -> mobile wheel. A lot of the current hot start-ups are just building web solutions around concepts that where available on the desktop. Albeit with some innovations, but there where accounting systems before mint.com, a developer that has 20 years in accounting software experience, I assure you, is not going to get in the way.