"The average airborne operating cost of a Boeing 747-400 is between $24,000 and $27,000 per hour, around $39.08 to $43.97 per mile, using approximately $15,374 in fuel per hour.Apr 5, 2015" [www.opshots.net/2015/04/aircraft-operat...
And it takes about 13 hours to make the trip. So the total cost to just operate (fly) the 747 one way is $325,000.00. Divide that by 500 seats and that's $650 per seat on average.
So by your numbers, coach isn't even paying to cover the average costs for flying. Which means the fewer First and Business Class seats have to pay more to make up the difference. Just to cover operating costs.
Then there is the obligatory profit margin to pay off the stockholders and owners of the airlines. That has to be pro-rated and added onto the price of a seat.
Frankly, those numbers you cite sound cheap to me. You're lucky they're not higher.