AT&T's $200 early upgrade fee & iPhone eligibility

Well that's a wet blanket.

After getting all excited about the iPhone 3GS announcement yesterday, I rushed over to the Apple online store to place a pre-order for a 32GB model only to discover that I'm not eligible for the $199/$299 (plus two-year contract, natch) pricing that Apple advertises.

After entering my account information on buyiphone.apple.com I get this message:

The problem is that the "early iPhone upgrade" that they speak of is actually a $200 penalty, making prices a little too expensive for my budget:

The weird part is the 12 July 2009 date after which I "may qualify" for a standard $199/$299 iPhone upgrade. According to AppleInsider AT&T won't subsidize the cost of another new phone by $400 after less than a year of service. An AT&T representative told me that iPhone 3G customers have to wait 18 months before being eligible to upgrade to the 3GS at regular prices.

I purchased my iPhone 3G on 08 June 2008 and was confused by the 12 July 2009 date show above. Why are some iPhone 3G's eligible for an upgrade after 13 months while others aren't eligible for 18 months? A blog post at iPhonesTalk thinks that it's a wrinkle with the AT&T family plan and explains how to swap iPhones among family:

...sometimes the other member of family plan is eligible. So just get the 3G on the family’s members line, then simply swap the SIM card... It’s not illegal really; the same family uses it and pays the bill.

Another iPhone 3G on my AT&T family plan purchased on launch day (08 June 2008) is showing up as not being eligible for an upgrade until 12 December 2009 – corroborating the 18 month policy. A friend who purchased his iPhone 3G on 08 June 2008 was also given a date in December before being able to upgrade, indicating that 18 months of "eligibility" is required to obtain the 3GS at the $199/$299 pricing.

What are you seeing for eligibility? 18 months? Are you becoming eligible because of the family plan?