Your convertion, calculation only prove 1 thing. You lack of resource, and your respond is slow.
If we are talking about making gold/USD from Diablo 3, you are just.. 

Commodities are hot piece before RMAH commodities up.
Depend on RMAH/AH alone, you are way to slow to make gold/usd.

My Priorities Off-load Point (no blizzard cut)
- Gold selling site with item sell. ( i sold some gems to them, USD49. they able to sell at USD80-90 )
- playerauction
- Blizzard Diablo 3 Forum - Using Paypal
- Ebay ( the more you post, the more you get )
- Non official Diablo Forums
- Trade Channel
- RMAH
- AH

Rolling Gold into USD
Buy gold from Farmer.
Build up blacksmith ( when i said build up, is not level up the smith. i spend more than 50m on recipe - 2 +6prop cost me 35M already )
Gathering Materials from AH
Mass producing.
Godlike - Forum / playerauction / ebay ( post a copy every corner the world, dont put in RMAH, avoid 15% cut )
Good - Sell in RMAH ( to push RMAH sales, use trade channel + D3 official forum )
Middle - Sell in Trade Channel
Low - AH
Useless - donate to players
Commodities - high level gems - Selling at website/Forum/ebay

Diablo 3 not worth my time playing. but playing the item-trading is superfun & profitable.

You are professional farmer. ( hard earn gold )
I play it like a businessman.

thats the different.