If you've done any online shopping you've likely seen items listed as "Grey Market" or sometimes as "Imported" and usually for a lower price than identical items for the USA market.
It can be real tempting but let me tell you before reading any further - don't do it for Nikon products.
The big problem is that Nikon no longer sells most repair parts to third party repair shops - almost all repairs go straight to Nikon regardless of the repair shop or facility you actually sent the item to for repair.
Here's the rub - Nikon absolutely WILL NOT repair or warranty a grey market item. The only exception is if you bought a camera overseas and you still have the receipt and can prove you bought it overseas.
Nikon knows the intended market for all items because they track them via the serial number and it provides an undeniable system. And when your item arrives at the Nikon repair facility the first thing they do is check that serial number, if it doesn't match up they box it up and ship it right back out and charge you the shipping costs. You end up paying shipping to and from Nikon and end up with the exact same broken camera you had previously. It's unlikely that Nikon will even bother explaining why they shipped you an unrepaired broken camera. It's grey market and they don't care. It's that simple.
There are some differences in how Nikon treats different classes of items, a camera body is treated differently than a lens or a flash unit. But overall you're gambling big time if you purchase a grey market item.
Here's another rub in the grey market. Some vendors, particularly on Amazon and most likely on ebay as well, will not disclose grey market items in their listings so you MUST READ CAREFULLY before purchasing.
Even still, you can do all the research possible and still end up with a grey market item. You can determine this by going to Nikon USA's website and registering the serial number. If it's grey market the Nikon web page will tell you.
This was not always the case, but the recent changes in Nikon's policy are meant to shut down grey market sales and that policy leaves you with no repair options at all.
So, you've been warned!