So are you against business and first class? Without those customers paying 10x the economy fare, average folk like you and me would never be able to afford to fly around the world. You should be very careful when deciding what kind of markets are good and which are "bad".
Each section of most planes bring in the same amount of money. So say you have 100sqft for seats the price is basically determined by 100sqft/seats. So while first class costs 10x much the 15 people in first bring in the second revenue as the 150 in economy.
The other consideration is that you'll likely not fill an entire plane if totally filled with economy seats so the price for everyone on an all economy flight would have to pay significantly more per seat to make up for the 60-80% capacity on basically 80% of routes.
