The Secret to Buying the Perfect Diamond

“I could find a diamond, grab that G.I.A. number and find all the retailers selling it,” he said. “There would be four or five retailers all selling it for a different price. It could be a $2,000 difference.”

In the end, he paid $15,950 for the two-carat round diamond.

“The biggest hurdle is not seeing it in person, not holding it,” Mr. Doyle said. “I don’t think it matters if you’re spending $5,000 or $25,000 — it’s a lot of money.”

And it’s also not like shopping for shoes on Zappos. “You don’t buy four pairs and see which one you like,” he said. “Even though the sites have good return policies, you’re tying up a lot of money.”

He was gratified when the diamond was appraised for $19,500. But for him, the true test will be when he proposes to his girlfriend in a few weeks.

Mr. Mobley from the Diamond Producers Association took a more nuanced view of the price difference. Diamonds, he said, are not dependable, presentable cars that will get you safely where you’re going. Diamonds are imbued with the emotion of the moment when they are given. Their value is physical, emotional and, over time, sentimental.

Quantifying that, Mr. Mobley said, does not always come down to which store has the cheapest gem. “It’s the total experience,” he said. “If you go to a jeweler with a great reputation and you pay $300 more, it’s all about that lifetime of service. You have to take that into account.”

Mr. Taira’s search was more about paying the right price for the diamond he wanted. Complicating the effort, he was looking for a larger diamond in a perfect condition. The price difference could be as much as $4,000 among various retailers.