MY AU55 1857-C $1 GOLD IS WORTH 2555 POINTS. SO IS AN AU50, OR AU58. WHAT GIVES?

POINT OF QUESTION. COMPARING SCORES BETWEEN XF AND MS-60 WE FIND THE GRADE AU. THERE IS AU50, AU55, AND AU58. I'VE EVEN SEEN AU53 NOW AND THEN. IF I WORK TO BETTER MY COLLECTION, EVEN IN THE SMALLEST AMOUNT I'D LIKE IT TO BE REWARDED IN SOME WAY. USING THE NUMISMEDIA RETAIL, THIS COIN INCREASES IN VALUE BY $4070 FROM AU50-AU58! I BOUGHT THIS COIN FOR 1200 IN A PCI HOLDER AS AU50. THOUGHT ABOUT IT FOR A YEAR, CRACKED IT OUT AND SENT IT IN. I GAINED AU53 AND AU55, BUT I STILL HAVE THE SAME SCORE. COULD WE GET A LITTLE HELP HERE? I ALWAYS LIKED MY WORMS FROM A CAN!