There are two types of data loss to think of: the minor loss of an important document or image, and the total loss of data from your computer
The minor loss of information costs an average $3400 dollars due to lost productivity, technical services, and for the actual value of the data itself[1]. Of course, if the data lost is a video of your childs first steps, or a photo of your clients wedding, then it is impossible to place an actual value on the loss as the data cannot be recreated.
The US National Archives & Records Administration states that 93% of businesses that suffer total data loss file for bankruptcy within one year. 50% of those business file immediately.
So losing your data could cost you quite alot. In the case of an Australian company you may also find yourself in breach of the Corporations Act for not preserving company data adequately.