Look, I'm not going to try to convince you that the Galaxy S7 Edge is a good phone. If you're reading this, then you're already interested in this kick-ass device, which I personally think nears perfection and can easily fill most people's needs in a high-end smartphone.
The S7 Edge also comes in a dual-SIM variant that's usually more expensive, and harder to find if you want it unlocked in the US. But if this is what you're looking for then you should stop and check out this eBay deal. A highly rated seller is offering the unlocked S7 Edge Duos 32GB for $599.99 today. That's $20 less than the last time we spotted a discount on the same phone. It's a new unit in unopened packaging and plenty of 3G and 4G bands that should work just fine on AT&T and T-Mobile — check the listing for all the details.
Shipping is free in the US (no taxes unless you're in Florida) and the seller is willing to send it over to other countries too, but expect to pay for shipping and import taxes if applicable.
Oh and just in case you want to shave off a couple more cents, another seller is offering the same device for $599.13. Shipping options and prices might be different though, so check it out as well.