I have done a few of these audits in the past. I also noticed that they haven't bonused them at all in my area, and there is no way I would do them for 15 plus 15. The first one I did was for 35 plus 15 reimbursement, and I decided that wasn't enough. The second one I accepted when the fee got to 55 plus reimbursement, and that seemed fair. The third one they called me last minute and paid a whopping 100 plus 15. That was awesome for about 90 minutes of work.
On a side note...at one of the stores the store manager followed me around during the audit, and the poor guy was so nervous. When they didn't have one of the advertised salad mixes on the shelf he totally freaked out. I felt bad for him, and told him that it's just one item, and everything else looks great so far. He confided in me that they got a bad report last time...and then almost in TEARS told me that these audits are "just another stick for corporate to beat us with". Ugh. I felt horrible.
Luckily, they had no other outs or any other negative issues, so hopefully they didn't get another beating based on my report.