The entire process is detailed pretty well on the official blog. The basic steps are
- In each Act, get 5 stacks of Nephalem Valor and then fight the Keywarden for a chance to collect the keys/plan. (You only need to get the plan once)
- Give the Blacksmith 12,000 gold to construct the Portal Device.
- Use the Portal Device in Heretic's Abode to reach one of the Uber bosses and get a chance to collect an organ.
- Purchase a recipe for the ring from Squirt for 2 million gold (only need to do this once)
- Give all 3 organs to Shen along with 15,000 gold to construct a ring.
So its a minimum of 51,000 gold per ring (3 x 12000 + 15000), plus a one time cost of 2 million for the ring recipe.