Ring prices in Europe vs. US - BIG gap?

Hi all,

First off, I did post this in another group as well. Kinda in a hurry
: )

I'm shopping for a platinum wedding ring set. 
I Holland I got a quote of €3700 for a set of 2 rings, 
6mm size 19 (US 9) and 4,5mm size 17,5(US 7,5).
Both rings with a flat top/outside and comfort rounded inside and are
2,5mm thick.
The 4,5 mm ring has a .13 ct princess cut diamond in it (quoted at
€320, grade unknown).

I got a quote from the US (NYC) for probably the same set:
Platinum, 6mm, 4,5mm, 0.13ct diamond, comfort fit, for $1600.
I don't know the "thickness" of these rings. 

Does anyone have a clue as to why there's such a BIG difference
between the two quotes, or is platinum generally a lot more common and
therefore cheaper in the US? And what about NYC, does that cut the 
price even more?

Thanks for your help.

D.