My reply is always 'please put me on your do not email list'. It's simply not worth the hassle. This is becoming more common around here. I have had several companies that continually email about the same project because they can't find anyone to do it. My response is always the same.
I haven't worked on one of these projects, but I don't see why you wouldn't just throw out a huge number and be done with it. Either it's too high and they leave you alone or you make what it takes to do the job right and put up with their requirements?
Because you're already busy enough that you really don't care how much money you might make on one of these "pain in the ASCII file" jobs.
Making money is a relative term, you can "make money" on one job and lose money on another, sometimes intentionally. There are times when I will basically give survey work away if the contract assures us the environmental, due diligence, engineering and stakeout. Whatever work I give away in the beginning becomes much more profitable in the long run.
Taking on a "pain in the ASCII" job makes no sense if you have a diversified firm who doesn't have all their eggs in one basket.