There aren't many hard and fast rules about who gets paid how much; but there are a few realities. For instance, in general, outside sales people earn more than inside sales people. And inside sales people generally earn more than tele-sales people. Do you know why that is?

It's simple: A worker's value is determined by his or her replaceability. Good outside sales people are harder to find than people who can wait for customers to come to them. People who know how to deal with customers are harder to find than people who can read a script into a telephone. The harder to find people have less replaceable talents, or skills.

Your replaceability is determined by how much rare or unique capability you bring to your work. This uniqueness is what determines how much you earn. If you can't be replaced because of your unique talents, then your customers have no choice but to pay more for you.