Bear in mind these things do not directly save any lives, and assuming they find the Air Asia DFDR / CVR soon, just save some search effort.
Salvage operations are expensive of course. The AF447 recovery cost around $42 million. More than $100 million has already been spent searching for MH370, making it the most expensive on record.
Source:
How crashed planes like AirAsia flight QZ8501 are salvaged | News.com.au