Basic laws of supply and demand.

There is more demand for software engineers, and they can generally be charged out at a higher rate.

Also there is a lot more diversity in software which increases the competition and pushes the price up. Don't forget all the guys programming embedded systems, fly by wire, weapons of mass destruction and so on.

One more thing network person are also supposed to handle the system administration things too. Does this thing exist in your part or not?
Yes, unless the network people are very specialised and there is another section looking after the more day to day activities of infrastructure support.