What is a 1.75 round cut diamond sI2-3 h color worth?

Whatever you have to sell is worth whatever someone will pay you for it.

You can purchase a diamond with these characteristics today on Blue Nile and spend between US$13,884 and US$19,165, depending on the Excellence of the cut and exact carat weight that you want.

If you own a diamond of this quality, best practices dictate that you pay a certified gemologist to produce documentation of the diamond's characteristics. This will support your research in establishing a market value for the diamond.