What is the average price for a 12 carat diamond ring?

Tens of thousands of pounds/Dollars.

Another Answer

The price of the ring depends on all the variables, including the quality of the stone and the karat value of the gold or purity of the metal used to mount the stone. For example, you can purchase a 12.35 carat, G colour, internally flawless stone today on Blue Nile for $94,049 per carat for a total purchase price of over one million (US) dollars.