It's a common problem for any small business owner with an e-commerce enabled website--clients and prospects abandoning their orders before check out.
Forget the wasted money in driving the prospect to the site. Forget the money lost on not receiving the order. The worst part is that you never got a chance to truly sell to an interested prospect that may have become your biggest customer over time.
In my own experience, I have clients that know their abandon-rate off the top of their heads. While it's great to be knowledgeable about these types of statistics, I'd prefer they focus on not accepting cart abandon as a "given" or part of the status-quo.