For startups, I'm pretty upfront about the fact that I don't negotiate but if they go under my activation price I will simply decline. It's a one and done deal and we can revisit months later. The range of cost I'll accept is quite large (though this part I don't communicate). I don't mind working for $200k annualized on things I really enjoy and I don't mind working on things I enjoy less for $800k annualized and so on. I have an internal sliding scale and I'm quite clear that I don't really need to work on any specific thing. Then I just take the gig if it meets my internal criteria.

In my experience, it isn't about making a $20k more now or whatever. It's about making a million more because you're invested in something worthwhile etc. etc.