They all vary, very hard to tell, but expect to spend at least $100-$500 if you ask me. And even then, no guarantees.
Now, the best thing you can do from now on, it is to have a backup, or just use MBL as the backup unit. Backup means you have 2 or more copies of the same data across multiple devices. Some nice reading:
http://howto.cnet.com/8301-33088_39-57556308/digital-storage-basics-part-3-backup-vs-redundancy/
Now, if you just want to recover/delete the data, the following guide will explain how to recover it up to step #2.
Be aware: This will void you warranty. As of matter of fact, check with support, since any action in which the case is open, voids your warranty, but it seems they are telling you otherwise.
http://community.wd.com/t5/My-Book-Live/GUIDE-How-to-unbrick-a-totally-dead-MBL/td-p/435724
And last, the above link it is to debrick/unbrick MBL, there are multiple guides in case you want to do it yourself.
http://community.wd.com/t5/My-Book-Live/GUIDE-Debrick-MyBookLive-v2-0/td-p/567582
