And I'm not 100% anymore sure if the upgrade status was set to instant eligible for the past year if they bought an iPhone, even if they bought a subsided phone right before it.
So, say 6 months ago. Just to be dark and probably would fail, but by this logic, could someone have bought an expensive and free subsidized regular phone, then buy the iPhone, instantly making them eligible again, upgrade to get another free phone , reactivate the same iPhone, instant eligible again, upgrade to a free phone, back to iPhone, again and again...
No. I this is the way it worked:
You could have bought a subsidized phone (if you were eligible) BEFORE you bought the iPhone. Then you could have bought the iPhone, signed a new two-year contract, and your upgrade eligibility was based on THAT NEW CONTRACT -- set to zero. So -- a very few people that were able to find an iPhone in May, could have first gotten a Blackberry (subsidized). then an iPhone (full price), and because they're on the iPhone plan now, they're eligible again. Those people are "luckier" than you (and me).
MANY people did not get a subsidized phone when they could have (for example, the switchers to AT&T who bought on launch day, who didn't first get a subsidized phone), and they STILL had to sign a two-year contract, and their eligibility date was STILL started from zero as of that date. So they WOULD HAVE had to wait another six months before being eligible, despite having paid full price. Now THOSE people, a full year later, have been made "eligible." Those people are "unluckier" than you (except they've had an iPhone for a year).
MANY people fall somewhere in between.
So -- some people may get a subsidized phone a bit more often than you, and some people less often than you. Like others said, life isn't "fair."
NO ONE could get a subsidized phone, then be eligible for another one in a month just because of buying an iPhone. You're right, that would be ridiculous.
Your worries that you won't be able to get a 3G iPhone for ANY price I'm sure won't come true. Look at the threads on MacRumors from 11 months ago. Some people thought that even at $599, only eligible customers would be able to buy. They were wrong. Just wait and see, and don't worry about people who actually got a good break from AT&T! It's not usual, be happy for them!