One of the last devices to currently sell with Android 1.6 is finally getting an update.  Dell’s site today advertises the Streak 5-inch Android Tablet with a Froyo update (and unlocked) at a $30 premium over the version that is tied to AT&T (T) with the older Google (GOOG) Android OS.

The 5-inch Dell Streak can operate like a phone, so it also includes a phone plan when purchased with an AT&T subsidy.

It isn’t clear why there is a $30 charge to unlock a phone and update it to the latest OS (which should be free).  Perhaps AT&T is paying $30 to have the Streak locked?  Nor is it clear why phones locked to AT&T aren’t getting the Froyo update as of now.  I’ve reached out to AT&T and Dell for comment.

Froyo is expected to be an over-the-air update for existing Streak owners at some point in the future.  Sony (SNE) is also rolling out Android updates to one of the only other Android 1.6 devices on the market, the Xperia X10.

Dell also released a version of the Streak in Cherry Red.