Victims of previous versions of the TeslaCrypt malware were lucky. Not in the sense that they were infected by one of the latest in a long string of new ransomware strains to come out, but because a bug in TeslaCrypt meant that the encryption key was stored on disk. That turns out to be pretty handy, when you can use said encryption key to decrypt the data that TeslaCrypt is meant to be holding to ransom.
Now, unfortunately, it seems the authors of the TeslaCrypt ransomware have learnt the error of their ways and issued a new version, which no longer stores the encryption key on disk. The result of this is that anyone infected with the new version of TeslaCrypt (version 3.01), have no option to retrieve their files apart from paying a hefty ransom fee.
The impact that this can have on an organisation, especially if multiple computers are infected, can be staggering. Apart from the costs of actually paying a ransom fee, the loss of service - especially if a core server has been infected - can result in huge losses to the business. The best counter I can recommend is to ensure that you have up-to-date, offline backups of all your critical data. Online backups could become victim to the same ransomware, so having an offline backup (it could just be a couple of external hard disks on a weekly rotation) that isn't connected to a computer 24/7 will at least allow you to restore your lost files in the event of an infection.
Previously, it stored the private key needed to unlock files on your own machine. However, after generating the key locally, TeslaCrypt 3.01 transfers it to the bad guy's server and deletes it from your PC. As a result, "the private key never has to leave the [attacker's] server and the ransomware uses a different key for each victim," according to Talos. With the 256-bit key nowhere to be found and impossible to brute force, the only way you can get your files is to pay.