How much is the price

Yes. Sales Tax in the New York is 8.875%.

With Sales Tax the price would be 761,03 $, for the 64 GB model. It's an additional optional 50$ for the 128 GB model / 150$ for the 256 GB version.

https://www.apple.com/shop/buy-iphone/iphone-11

If you buy an iPhone in the US, and you do not live there, and you fly back to your country and use your phone there, you will not have any warranty because it's limited to the country where you bought the phone, in this case the US.

The sales tax in NYC is 8.875%

To explain what Allan said, if you buy the phone in the US it will have to be returned to the US for warranty (or out-of-warranty) service. iPhones do not have international warranties.

A phone purchased in the U.S. will only be able to have any warranty service done in the U.S. if you plan to use it outside of the U.S. and you have a problem with it, you would need to return it to the U.S. for service repairs.

iPhone 11 features one physical SIM slot and one eSIM that you need to activate with your carrier.

See: iPhone 11 - Apple

It's 699$ in the US.

Yes, there would be local and state taxes applied.

Where is home?

If it is not the USA then an iPhone purchased in New York will have no warranty support.

The iPhone warranty is only valid in the country of purchase.

So if you don't reside in the US, you will not be able to get any warranty support on an iPhone purchased in the US.