In my four days of trips to the Saudi Arabia Consulate in New York I got to know 866 Second Avenue very well. The building primarily houses permanent missions to the UN plus the full consulates for Ethiopia and Saudi Arabia. One time the elevator stopped at the second floor and opened to the showroom of the Diplomatic Duty Free Shops of New York. I later had time to explore during one of my waits at the consulate when the staff asked me to step away during prayer time.
DDFS has locations in New York and Washington, D.C. that are open to the public. The NY showroom focuses on all the typical luxury goods except alcohol and cigarattes which are available from their hefty catalog. I did not do a detailed price comparison; prices seemed similar to other duty free in the US meaning not any particularly good deal. It could be useful as a stop when taking Christmas tree sweater wearing visitors around NYC, a way to look like a NY insider.
The advantage is for diplomats that can be exempted from NY sales tax, with the staff on hand to help out in the preparation of DTF-950 Certificate of Sales Tax Exemption for Diplomatic Missions and Personal.
The form lists exemption cards of Buffalo image, Owl image, Deer image, Eagle image, all issued by the US Department of State, and the American Institute in Taiwan (AIT) card. Some apply to official purchases, some personal. I should dig a big deeper some time, I imagine there is fierce competition among diplomats over who is a Owl versus a Deer, etc.