I sent my 64gb micro sdxc card into a data recovery firm to try to recover files recorded with my gopro hero 3 black edition
here are the results
Our lab has completed the evaluation and the card was found to have severe firmware corruption. The memory chip in this card is a monolithic technology which makes recovery highly complex (may be even temporarily unrecoverable).
We will need to do whatever is required to try to get a read from the memory card. If we regain access to the data, we will do a logical reassembly to try to put the files and directories back together to get them as close as possible to their original state. At the end of the process, we will provide you with a file list to review so you can approve the completion of work.
The cost of the recovery will be $950 and the estimated time to complete your case is 9 business days.
End of Quote