I had wanted a Tiffany ring all my life and yes, I admit I was sucked into the marketing blitz of the little blue box. Having said this, nevertheless, I did extensive research when the time came for me to buy the ring. My SO and me went shopping, stepping into Tiffany, Cartier, Larrys, Lee Hwa, Soo Kee, independent jewellers like JP, Canary etc etc. We stepped into each store at least 3 times each and did extensive research.
Summary of our research, for a certain range say 0.5-1c, branded rings such as Tiffany and Cartier are actually priced pretty much on the same range as local/independent jewellers. And we were looking at platinum setting.
Granted that their specs may be slightly lower, say an E colour compared to a D colour, everything else the same, Tiffany and Cartier may cost a couple of bucks more.
Talking about full retail prices here, prices are actually pretty close between designers and local jewellers.
Thing is local jewellers always have sale, thus making the the rings a lot cheaper.
In the end, we went with a Tiffany and my SO had so many people telling him he was dumb not to go for a bigger/better ring for the money he paid at Tiffany.
His answer? "It's about giving her what she wants and not what others or I think she should have.".
We may have made an illogical decision and people think I'm just dumb to get into all the the marketing hype. But at the end of the day, buy the ring that calls out to your girl, budget permitting.