Well, getting $1500 is a bit of an overstatement. I tutor like 25 hours a week and I'm nearly really occupied (that's saying something, i'm not even going to uni this year since I graduated). It's easy to do the multiplication, but you haven't taken into the fact that are there really that much students (especially if they charge over the market price) and the time to travel or the time to match every students preference, because they can only tutor after school (and hard to tell them to come like at night). That leaves like only 2 hours each weekday for like really normal lessons of more than 1 student and like 8 hours weekends if you can really squish it and everyone is willing to come.
But I agree to charging over $40 for just those credentials is really over-pricing, because those credentials never really prove you are a good teacher/tutor. Students know after a few lessons anyway and they start to change tutors. So if you ARE an economist, you should know how economy works, there are competitions and no one can bump up the supply's price and get the same quantity. There is also a demand curve in the economy.