is what this is

15:29 Aug 20, 2014 

I think there is a very subtle difference here. The Sally example is indeed emphasis but the example in the question is more of an explanation. X thinks it is a good thing, Y is preparing to explain why it isn't. I agree that the difference is subtle but I think it is there. I had my doubts when the question was first posted because of the second part of the last line. The extra context reinforced my doubt.

15:23 Aug 20, 2014 

I agree with BD Finch, that this expression is used for emphasis. You can think of the sentence as reading:

If you want to know what this is, it's a big pain.

Of course, this changes the meaning slightly, but this is just to understand the unspoken intent behind the words.

Here's another example using the same structure:

Q: What's Sally doing?

A: Sally is making a big mess is what she's doing.

In other words: If you want to know what Sally is doing, she's making a big mess.

There is often a hint of sarcasm or anger in this structure. Imagine, for example, Sally's father is calling his wife to check on their daughter Sally. He asks an innocent question, but the wife is upset because Sally is making the house messy. The implication is: You might think that Sally is napping or quietly watching television, but what she is actually doing is making a huge mess.

Same thing with the example you provided. One might think it's a good thing to have more business and to make a big sale, but the truth is that this is actually a pain.

14:58 Aug 20, 2014 

Sorry, I hadn't noticed the last two questions, only the first three, which is why I was a bit lost. I spent a good 10 minutes re-reading the first three questions, trying to spot the extra context!

14:48 Aug 20, 2014 

There is additional context in another question by the same asker.

I don't actually know that the one worker is older but the additional context makes it clear that he has been working at the company for a long time and has seen this situation enough times to infer a pattern.

14:42 Aug 20, 2014 

I think I'm missing something. How do you know that one of the employees is older than the other? How do you know a sales rep has been dishonest? How do you know the goods will be returned?

As I understand it two people have to load goods (presumably onto a lorry), take them to wherever they have to be taken and then delivered to whoever has ordered them. More money for the company, but more work for X and Y.