It's certainly a gamble. Pay $50,000 and possibly get back up and running or refuse to pay and lose valuable time and possibly go out of business.
Here is a good article on the subject:
http://www.denverpost.com/2016/10/23/small-companies-cyber-attack-out-of-business/
You are correct, sometimes victims pay and don't get an encryption key that works. For many businesses, paying $50,000 is worth it for a shot at getting the ransom ware lifted. However, it usually takes a while to buy bitcoin if you don't have any and don't have an account, so it's worth holding some so you at least have the option to act quickly.