You looking at the buyout prices. You can easily grab even a better pair via bidding. Dont stare yourself blind at AH prices. There is many factors.
The overall point still remains. Your both naive and in denial if you think, that character will gives 1 billion gold.
And you can for certain expect the value of each item, will drop day after day. So the longer you wait being realistic, the more gold you will lose.
And how exactly is that relevant? There's a reason the cheapest innas pants with similiar stats are listed for 40 mil buyout. A lot of people never even buy things off bid.
Also, I looked up the prices myself at the AH and it seems your estimations are a bit off. In fact, some pieces are worth double the amount that you've listed. I dont like this guy, and I think he's being insanely naive if he thinks he can get 1 bil for his char, but what you're doing right now is equally disgusting. It's obvious that you intentionally undervalue his items just to prove a point or to win an internet argument. I've been playing the AH basically since the game launched, and I think it's safe to say I know my way around it. For starters, his helm, boots, belt and legs are worth close to or more than double the amount you listed. His weapon is probably closer to 120-ish, his shoulders I would say around 30, lacuni 60, natalya 60. Of course, prices are dropping each day, but this is how much they are valued today. I'm pretty sure that he could get around 600 mil for everything, including gems, after the 15% if he sold it on AH right now. If he sold it for less than 500 off AH, I'd say he's pretty dumb.
You seem to be an inexperienced AH user. The prices i made are for real. I even added an extra 50m for the sake of double res. Some of the prices i set, you could even get a better version compared to his current. Tbh you could get a better gear set and weapons for under the 500m i set.