Buy James Campiglia's Official U.S. Casino Chip Price Guide and it will give you a wealth of knowledge including all the Rariety Values and the quantitys that make them common or rare, Its full of great pictures and will answer alot of your questions. As for one seller selling more than another, yes feedback helps but repeat business from customers sure helps too. Make a customer very happy and you will see them again. Some sellers have a great reputation for selling Quality chips for a good price and some buyers add them to their favorite seller list and often bid just from their favorite sellers and might not see your item. I dont know all the reasons why some sellers get more money as this is only my opinion. goodluck, I hope I helped in some way. John R-6920