The Galaxy S7 has been out for a while now, and it's about time the price started dropping. After all, it's not the only 2016 flagship out there. You can pick up the unlocked GS7 (G930F) on eBay for a very competitive $559.99. That's $70-80 cheaper than the price elsewhere and much cheaper than the US carriers.
This is a GSM/LTE phone, so it won't work on Sprint or Verizon. You should be good on any GSM network, though. 3G will only work on T-Mobile in 1900MHz areas, but AT&T will be fully supported. LTE is solid on both, including band 12 on T-Mobile. Also keep in mind this is the Exynos version of the phone, which some would say is the more desirable variant anyway.
The seller only has the gold version of the phone, but you can't argue too much at this price. Shipping is free in the US, and international shipping is an option. Tax is paid only in Missouri.