I have a client whose forum was recently taken down due to an inordinate amount of spam. After I sifted through their entire database from the only working backup their hosting provider (Bluehost) provided, I determined that all the posts had been lost.
They told me that they had paid for Bluehost's "pro" backup service to keep the site backed up, but I checked and explained to them that Bluehost's "pro" backup service still doesn't keep more than a month's worth of backups (the only thing their "pro" backup system adds is the ability to restore individual files from the web console).
I have an incidental backup that I made when I was last brought in to clean spam out from their system, and this has most of the missing posts. Due to their negligence in their own backup system, I am the only one who can provide this backup. How should I determine the price to restore their missing data?