According to this http://en.wikipedia.org/wiki/List_of_minimum_wages_in_People's_Republic_of_Chin a, it seems that 3-4 times is actually way to low, but what does a chinese farmer actually get in wages? As per https://netfiles.uiuc.edu/dtcook/www...er/7-2/jin.htm, notice it is from 2006 tho, so the minimum wage will be higher today.
So with those figures (the low end figure being bumped to 71.5 USD) we are looking at an average of 135,75 USD/month for a farmer(This being the average I'm including electricity, food, hosing etc in those numbers aswell of course), now if you look at how these shops are setup (Reference the above mentioned link) you have 2 persons working 12h shifts at the workstation, so we have an estimate of 271,5 USD/month or in order to make this a profitable venture you need to have each farmer produce 0,37 USD/Hour.
Now the numbers from beta suggest it is at the very least possible to farm 20.000 gold/hour which would put the gold to USD price at 0.18 USD for 10.000 gold for break even scenario, let's just say 0.2 USD for the ease of calculating it , so in order to make 10 USD you would need to sell 500.000 gold (and that's without the blizzard and paypal cuts) or in beta terms 25h of farming. Now we don't know what the gold/hour ratio is going to be later, but for the first 24h after release, if you did nothing but farm farm farm for those 24h straight you'd end up with 10 USD, you could mow your neighbours lawn in 30min and make the same amount I figure
With the amount of players, both "legit" and farmers, I assume the amount of gold coming into the system will be massive enough to keep the dollar price of gold near the break even point.
But how much money can we expect to come into the system, we can't really say, but let's look at the numbers from the link before. So a somewhat big chinese workshop has 100 workstations, now again with the numbers suggested we are looking at 48.000.000 gold coming into the game from that shop each day. Now factor in multiple workshops and the normal players making more money than they spend repairs etc... Gold will never be in short supply and as such it will be at the price where the 100 man chinafarm is "just" making a profit, see they can't raise their price because there is just another 100 man china farm around the corner who will sell at the lower price.
Based on researched wages from china farms and beta gold/hour, price of gold will be around 0,2$ for 10.000 gold initially