Writer wonders if a royalty arrangement for a writing project makes sense

Q: In my quest to attain new and interesting projects I’ve been solicited by this company looking for authors to write 45-55 minute instructional audio books on CD/Tape, but
they’re only going to pay royalties of 15% each unit sold. I’m leery about this and I’m wondering what your take might be. From what I’ve read, this kind of project should net from $3,000 to $8,000+. Does this seem a feasible revenue-generating project?

Q: If all they’re offering is potential royalty for your writing time, I’d run. Fast. This is a business we’re in, not a speculative venture. Especially when you have to rely on their marketing to make it happen. Forget it.