Although goods may be cheaper in developing countries, the level of pay relative to their weathy country counterparts is much lower. Indeed, many workers live below the poverty line despite possessing jobs. The price of goods in those countries are still high enough so that these people cannot sustain themselves at a higher standard of life.
A few years ago much was made of the concept of "small donations" where even a tiny amount of cash could help someone living in a third world country start a business and get themselves out of poverty. I think it's time to continue this trend and possibly even donate more money so that we can increase the benefits that people in third world countries could gain from such donations.
Paying them more will not only allow them to afford to buy the good that they need, but it will also help to boost the world economy. They will buy more goods, which will allow more to be produced and to create more jobs. The job market will also become more competitive which increases productivity.