For this particular case you were charged for the recovery attempt on a Damaged DVD - This involved an engineer using equipment specifically setup to read the data streams on DVD. Despite the resources and time the data fragments we could read could not be reassembled into a working video.
The reason for this was given. 1 side is unreadable - corrupted/unfinished write session.
Although £129+vat is an expense no one wants, as a lab we incurred much more cost in the attempt to help you. We work hard to get every recovery and we do not give in easily but we do have to cover cost of time in situations like this.