Just discovered this thread. Ppl in the industry will tell you - the HDD have spares sectors to cater for bad sectors - when bad sectors start showing up in SMART, the spares have been used up and your device will likely experience slow downs and slowly lead to not able to be detected, or knocking.

Rather than spend thousands on data recovery, why not go and buy a new HDD/SSD and back up the data? Saves you the headache later. Many have lost years of photos to hard disk failures, but cannot afford to pay to get them back. Ball is in your court.

Don't hope, do what is within your control, like you mentioned, back them up to the external drive. If not enough space, back up the most important data first.