The injection molding business is based on heavy investment, therefore the machine rates you will find worldwide will not vary too much, assuming you are comparing apples to apples. Some molders have very old machines, especially in third world countries, and can afford to charge a very low hourly rate for the machine time. However, beware, these low cost machine rates may also come with quality issues.
If you are looking for low cost machine rates, look for them in the vecinity of where the product will be assembled. Going to far distances will result in additional follow-up and shipping costs to where low cost machines rates may end up costing more.