It’s often the case that a temp recruiter will work at a percentage margin or mark up.  There’s no problem with this in itself, but it can lead to us losing track of exactly how much a percentage point means in cash terms.  So try to ensure that however you negotiate you are mindful of exactly how much money you are giving up when discounting – 1% or 2% might not sound like much, but when you work out how much that might cost you on each future deal it soon stacks up!