The current Foxcon worker makes about 400 a month supposedly so if we doubled their wage to 800 or even tripled it to 1200 the cost of the iPhone might up 100 dollars (that is a high estimate).
It might be in Apples best incentive to raise their workers wages (it allows them to afford what they are makingbasically putting money back into the company, also many in China who are coming into middle class might see Apple as a loyal brand for their progressive take on workers rights/pay.
Unfortunately, these workers aren't Apple employees. They are Foxconn employees. Apple contracts with Foxconn to build their computers and iOS devices, and Apple has no control over Foxconn employee wages.
In addition to Apple products, Foxconn contracts with many other large tech companies. These same workers might also work on product lines for Google, Microsoft, Nintendo, Amazon, Motorola, Sony, Cisco, Dell, NOKIA, HP, Acer, etc
(Source)
http://en.wikipedia.org/wiki/Foxconn