I'm answering this a little late, but I just can't let this one go by.
Publishers seem to be trying all kinds of funny things these days, and
asking an artist to do 250 illustrations in a month is mind boggling. Even
a quarter of that would be near debilitating. I would insist that
compensation be commensurate with the task requested! In other words, bid
high, and tell 'em why.
I don't know who the publisher is, but I am hearing about newer companies
who don't have a clue about artist's rights, and who want it all for a song.
They immediately set up an adversarial relationship with their artists by
insisting on these awful contracts which leave the artist with virtually
nothing except a modest pittance at best. Try not to give up your rights,
or at least discuss them openly.
These companies also pit artists one against another by making it known to
all prospects that they are 'fishing for bids', and thereby psychologically
setting the stage for a price war. That's not necessarily bad, but there
are many more factors to consider above and beyond price.
In making your bid, emphasize those things, such as 'service', 'cooperative
spirit' , 'accuracy', and any other non quantifiable item that could make
your higher bid worth a second look.
Please let us know how this goes--I'm interested to hear people's
experiences in the changing publishing market.