How much would it cost to put a 1kt diamond on a ring?

My mom has 3 1kt diamonds for each of my brothers and I. She has already given the diamonds to my brothers to use as engagment rings however I would like to have the diamond put onto a ring for myself. She says it is currently on a necklace, but I prefer a ring...she has saved it for me for over 20 years and I want to make it a specail ring for me. She has given me suggestion to have three smaller diamonds put around it on the ring however I would like to just have the diamond by itself. I'm not sure if 1kt is substanial enough for a ring but I do know my brothers ring was goregous and was perfect... Does anyone know about how much it woul cost to have the diamond made into a ring? I'm very wary of going to a jewlery store and want to know what to expect... my mom and brother told me that it did not cost much to have my sister in laws engagment ring made but they haven't given me figures. I've been saving up for the last year and want to do it sometime soon. Anyone have suggestions?