It's great, except you have to factor in all the deductions and expenses.
Not only are there all the taxes, royalties, and regulatory compliance costs, but there are operating expenses. A ten barrel a day well isn't flowing to the surface by itself. It has a $100 thousand pumpjack. Maybe more or less depending on the depth where the oil is coming into the wellbore.
It doesn't get to the surface for free.
If you have to schedule a workover rig to go out and work on that well making $500,000 a year more than once a year, you're going to go broke.