Right on time, as previously announced, today is the release date for the unlocked Galaxy S8 and S8+ models in the US. We're talking about the officially sold versions of the two, keep in mind. You can find variants meant for certain international markets on eBay, for example, and those are indeed cheaper than the officially sanctioned iterations. However, if you go that route, you may be giving up proper after-sales support, and might also run into issues with things like not all of your carrier's bands being supported. If paying a little more for the peace of mind that you won't have to...
Source: http://www.gsmarena.com/unlocked_samsung_galaxy_s8_and_s8_are_now_officially_available_in_the_us-news-25351.php