Publishers and compensation

Along with all the remodeling and traveling that I've been doing this summer, I've also been working with a textbook publisher to help create supplemental materials for the upcoming release of a biology text. The work has been focused around two projects: writing test bank questions (as well as helping organize the test bank for the book) and helping create a lab manual to accompany the book. These projects both mesh well with my own teaching, as I can always use more test questions and I need some labs for my new course anyway.

However, one thing that's awkward about doing this work is the compensation. I like getting paid for my expertise, but I don't quite know what to say when the publisher talks about compensation and then asks, "Does this amount sound reasonable?" I don't necessarily feel undercompensated for the work I've done so far, but on the phone yesterday morning the publisher doubled my pay for one small portion of the project on the spot, without prompting from me, which tells me that compensation in this field is pretty flexible.

Additionally, they (the publisher and my lab manual co-author) want to incorporate some of my own labs into this new lab manual. I'm ecstatic that they feel my labs are good enough for inclusion, but I have no idea what kind of compensation to ask for or expect in return for the rights to the labs. They've said that they typically do up-front payments, but that they might consider other options (e.g. royalties). My completely uneducated leaning is that royalties would be better, but they haven't given me any hard numbers yet so I have no idea how to compare the options (or even what numbers to ask for so I can compare the options). Actually, I don't even know what my options really are (though part of me is tempted to just make the labs open-source). I somehow missed that "How to negotiate with publishers" seminar back in grad school; guess I'll be getting a fast lesson in it this summer.