Textbook editing & design rates

Hi peeps. Looking for advice (as usual). A business English teaching firm wants me to edit and, I presume, lay out some lessons and textbooks for them.

Part of the job involves writing and designing lessons for them. The sample lesson I supplied came out at around 1600 words. They are offering 2500 per lesson.

The other part would involve editing and laying out 12 lessons of 4-6 pages each, supplied by their tutors, for which they have offered 5000 per project (all 12).

These rates are … problematic. At my regular word rate, I would charge them 10000+ for just the copy for the sample lesson I supplied them, let alone laying the thing out in an attractive format.

For project managing, editing (which I presume would be minimal, but who knows?) and designing their supplied lessons, my rough calculations point towards a figure in the 25000 mark (conservatively).

Anyone have local experience with this sort of thing? I don’t know if these folks are clueless, just plain stingy or trying to low-ball me hard to see if I’ll take it. What is the normal rate for this sort of work here?

Any advice would be appreciated, as ever.

No experience in Taiwan but I worked for a publisher in Seoul and they paid me $200 American for each 1,000 word story and paid $30 per hour in office for editing textbook lessons written by Korean English writers. That was 14 years ago.