Getting Hard Drive Data Back Full Of Videos And Photos

During lockdown I had tried to sell a macbook as I got a new laptop so sold the macbook to someone that could use it for something more usefull and was going to reset it but in the process had corrupted it's OS system files and then trying to get the OS back using the hard drive with all our family photos and videos the OS we installed onto the drive had formatted the photos and videos and then trying to get it back with software it had not gotten all the contents with only like 20gb of 1.5TB of contents were saved and then so given it to an expert to try and fix but will cost $675 plus GST for deep forensic to try and get back the contents. All help is considered