Hmmm.. good question.
I'm not magazine published so I can't answer the 'how much have I been paid for a magazine publish' question. I only made my first ever submission two days ago! To a non-paying market, I'll add, which leads to the next question.
How low am I willing to go?
Well, as you point out, poetry rates are so low that to me they are as good as pointless. My poetry, even the ones that don't take long to put on the page, represents a lifetime of experiences that led to me being the person to write that poem - 2 cents, 2 dollars, 20 dollars, it is all nothing compared to that.
No, what is more important to me is the prestige of the publication, and/or the true readership. 'How impressed will other magazines/publishers/peers be with that credit?' and/or 'How many real people of a type I'd like to reach will this publication help me reach?' I'll also add that it is important to me to read at least one sample issue - yeah yeah yeah because I'm supposed to in order to 'get what they want', but honestly I usually get that from their submission, mission or about statement - I read the sample issue(s) because I want to see what company I would be in. If I don't like the poetry they publish I wouldn't send mine to them - if they have more than one typing or grammar error in the entire issue then I won't send it - I don't want my name tarnished with their poor quality.
BUT - and it is a big BUT! in fact....
BUT if I feel that the magazine/ e-zine is making significant profit (or even just run by profiteers) then I would expect my share too. I don't mind not making money on my poetry but if I don't nor does anyone!
Anyone thinking they can make a living, or even just holiday money!, from publishing poetry is living in a dream world. What IS possible, though, is having published poetry legitimately, hopefully with a competition under the belt, and perhaps a couple of chapbooks or a real book (and earnt peas for it) would be to set up writing classes, and go on a talk circuit, and maybe even become a resident poet for somewhere - and that, friends, is the only serious money you'll ever (if ever) make from poetry.
So - relax about the immediate pence/cents per poem - and think simply about building a reputation as a poet.