Apple is now selling the iPhone 6 and 6 Plus SIM-free in the US

Fancy a new iPhone, but don't want to be locked in with a specific
carrier? Good news: Apple today started selling SIM-free versions of its
iPhone 6 and 6 Plus.
Prior to this, you had to choose a two-year contract or buy one of them
unlocked with T-Mobile. Thankfully, that's no longer a problem. The
SIM-free versions start at $649 for the 16GB iPhone 6, climbing up to
$949 for the 128GB iPhone 6 Plus. Apple has taken a tad longer than usual
to offer the unlocked versions, both online and in-store. Of course,
you'll still need to sidle up with a carrier, but at least now you'll
have more control over the contract you choose.