To answer the poster's questions: Yes, you can get an accurate replica of the tiffany 6 prong solitare setting from many other vendors. Is the Tiffany & Co. maker's mark worth the markup? That's hard to say. Most on this list would probably say no, but a few would disagree.
To provide a counterpoint to the esteemed Oldminer, for whom I have the utmost respect (and trust, as I've sent him diamonds to appraise in the past!)
Whether or not Tiffany diamonds depends very much on your frame of reference:
For the typical Pricescope participant, the comparison is generally between a 7 out of 10 Tiffany diamond or a 9+ out of 10 diamond from elsewhere for much, much less. In other words, NEVER Tiffany.
For your typical consumer (the other 99.9%), a 7 out of 10 Tiffany always beats a 3 of 10 typical "maul" diamond, but the tradeoff becomes price vs. quality. And with Tiffany vs. Zales, for instance, the Tiffany diamond is probably better and therefore might be worth that extra markup for the perception of quality. Never mind that the average consumer has no perception of quality and is probably being lied to at every step of the process...
So given the choice between Pricescope diamond & Tiffany diamond? Pricescope all the way.
Between Zales & Tiffany? Probably Tiffany.
But the bottom line is, the more you know about what you're going to buy, the better deal you're going to get no matter where you shop.