Salaries, especially in the startup world, are known for following no set rules.
They depend first of all by the stage the company is in: bootstrap, angel funded, vc funded etcetera.
Several investors told me, and i agree, that a funder should always ave at least a minimum stipend, even at bootstrap level, so he/she can focus 100% on the company. I tried working with co-funders that were less fortunate then me, and had to at least have a part-time gig in order to survive: not good for the business...
When you ask about C-level, i am assuming that the company got a minimum funding, and it is generating some sort of revenues. Although there is no set rule, if that is the case, and if the people are willing to, i would go for the lower side of the salary bracket, or for what is their minimum acceptable, and work the rest with equity (skin in the game) or bonuses (incentive to reach goals).
Just keep in mind that the sacrifice needs to be across all the C, so you don't create disharmonies.
When the company will reach set milestones, then you can change the salary to a more appropriate one.
Hope this helps. :)