Hi ladies!
I just bought an engagement ring from Tiffany's (classic setting) (to replace my stolen original) last October, and then upgraded it last week! So I can definitely offer some "expertise" in the Tiffany's diamond dept!
The thing is, it TOTALLY depends what quality stone you want. I looked at a few that were 0.09 carats difference last week and were $9,000 apart just because of the colour grading - and that was going from a G to an I!!
(One big piece of advice I learned by the way in my research? At Tiffany's they are all excellent cuts and below 2 carats, it's very hard to see any flaws with their diamonds with the eye... so for ME, I felt really safe going to their lowest which I believe is VS2 and spending more money on the colour grading. Not everyone can see colour as well as I can but I looked at a G, H and I last week and I could tell the difference between the H and I... so I ended up springing for the G. But go for colour!!)
Here's some stats I looked at (Canadian dollars, so would be slightly less in USD - maybe 5-10%):
My original classic was:
1.26 carats, G colour, VS2 was $16,800
I was also looking at a:
1.39 carats, I colour, VS2 or VVS2 was $14,000 (bigger stone, lower colour grade)
1.14 carats, G colour, VS2 I think for $15,000 (I think)
When I went in last week I asked for something between a 1.4 and 1.6 with a good colour grade (I don't think I can afford a D or E!) and they brought out:
1.59, I colour, VS2 - $21,000
1.59, H colour, VVS2 - $29,500
1.5, G colour, VS2 - $28,500
I ended up getting the 1.5 G colour one and am soooo happy!! Picking it up next Tues or Wednesday!!!
I could have gotten a slightly bigger one as you can see, and for much less money - BUT I can tell the colour and my band is a Tiffany's shared setting which is always F/G colour... and I could spot the I next to it. For 0.09 difference in size, I decided to get the G over the H colour. When I asked two of the SA's in the diamond dept what they would do they all said "Oh yes, for 0.09 you will never see the difference, go for colour!" I feel really good about my decision. I would have gone to an H to get 1.5 but didn't need to!
SO... basically you could probably get a pretty huge (1.6) Tiffany's diamond for $22,000 IF you don't mind I colour and their lowest clarity (which is still going to be one hell of a beautiful stone from Tiffany's!) And I'm sure you could get a 1 carat for under $10K if you didn't need a DEFG colour.
The more you care about the colour and clarity the more you will pay - there is no simple "$10,000 per carat" formula. I basically went up exactly 1/4 carat from the 1.26 G to the 1.5 G and paid about $11,000 more because for a G colour diamond there, it's more than $10,000 per carat - more like $20,000. But G is pretty much in the middle of their colour scale - I'm sure if you got an E it'd be even more per carat! Again, the lower you go with colour, the bigger a diamond you'll get. On the website it says "1.5 classic setting FROM $20,000" - so what they are doing is giving you the lowest "quality" stone THEY sell (which is still really good but is probably I colour and VS2, excellent cut) you could get for that carat. It only goes up from there!
And as all Tiffany diamonds are excellent cut (the most important "C"), I wouldn't worry too much about going down to a VS2 unless you are getting one big honking 2+ carat diamond!!
Hope that helps!!!
The best thing to do is go in and get them to write down a few for you, go home and really think about what you want and what's important to you. Also, they can bring them in from all over the world as long as it is in their system... so they could probably find you a 1 carat in an H colour, for example, somewhere in the world if that was what you set your heart on!
Good luck!!