Feel here to make money and pay is not proportional, often pay labor than earn money big dozens of times, so it is difficult to make money in DT! . Here just hobby photography, recreational entertainment.
All agencies are seeing a decrease in sales. Those agencies that developed a department store approach are seeing less sales due to unsustainably high price points. Also, very few professional photographers make a few hundred dollars per sale. That's the exception. The average is much less. Don't worry about others, just continue to build your own portfolio and be happy with your earnings. My sales are consistent because I add to my portfolio regularly.