People with Jobs as Sales People/Agents/Representatives (but not Telemarketers) (United States)

I work in a smaller office and the goal is to bring in sales dollars. I have been the top producer continuously for the past three years, however, because three individuals were fortunate enough to get hired by my boss prior to me they earn a higher wage. Our year end bonus is paid as a team as well so they make the same bonus as me whereas i have brought in more sales that two of them combined. I have tried to negotiate a fair salary for myself with figures to back it up but without success. These three ladies still earn between 5,000-8,0000 more per year. It hardly seems fair to me and I have since had a bad attitude. My solution is to seek other employment where I can be valued based on production as this is my strength.