You've heard of the book The Well-Fed Writer, I'm sure. Well the ladies at the Renegade Author interview its author, Peter Bowerman:

Your first two books (The Well-Fed Writer and TWFW: Back For Seconds) are aimed toward commercial writers. Why is commercial writing such a lucrative market for wordsmiths? As mentioned, it's where the money is. Businesses have more money and put a high value on good writing. Magazines don't have the budgets, unless it's a top magazine and you’re at the top of your craft. Right now, I'm working with a $250 million company, and paying me $125 an hour to get a job done right is a no-brainer for them. Those $50-125 an hour rates are just the norm in the commercial field; that's what it pays!

I have a friend who's a successful magazine writer who does a healthy amount of commercial writing as well. As she sees it, commercial writing doesn't take as much writing skill as magazine writing. While I think you have to be a good writer to do well in the commercial field, by and large, I agree with her. Plus, as a rule, you don't have to fight to get your money in the commercial arena, something far more common in the magazine world. I have never in my 13 years of commercial writing not been paid. In the overwhelming bulk of cases, I see my money in 30 days or less.

More here.