Finding an lower cost technology partner can be a difficult challenge. Just because a country has lower salary costs does not guarantee that you will save money by moving your software development there.

If it takes them a lot longer to do the work then it may end up costing more.

Many so called low cost suppliers greatly inflate their estimates in order to increase their margins. If you look closely at estimates you will find unnecessary resources that have been added to the project or worse yet just hugely inflated effort estimates.

It is always a good practice to get several estimates for your project. I often find it is not unusual for estimates to range from X to 10X for exactly the same set of requirements.  Often the low end company has underestimated the requirements. But also, the high end estimate has gold plated the requirements to eliminate any and all risks. The correct answer is somewhere in the middle, most likely closer to the low end.

Given the huge disparity in hours estimates it is not uncommon for the company with the highest day rates to be the least expensive option. They may have higher quality resources that can deliver quickly.

Because of this dilemma, it is very important to have a trusted supplier list and to make them bid against each other. It keeps everyone honest and gives you as the client the best chance of success.