Modern air transports are a necessity but they are not cheap and you have to look at what PAF requirements (guess work) are and then try to determine what aircraft might be best suited for its need and budget.
As far as C-17s go, there are none available as its no longer in production and too big and expensive for PAF's need anyways since its meant for strategic airlift. In Pakistan's case its size and range are overkill and will be underutilized.
Here are some of the options we have to look at. I will try to list them in the order of most likely and best suited in my opinion:
C-130E/H ... best bang for the buck are used C-130s. For example, we bought 5 ex-Australian C-130s from Lockheed for just $64 million, and they have been undergoing, along with all others in PAF, major avionics upgrade by Rockwell Collins for under $100M. So C-130J capability for the price of two new C-130s for 16 aircraft.
CN-235/CN295 ... still a requirement as PAF only bought 4 of the original 20 some it wanted to buy. Ended up buying some C-130s after that but the requirement is still there for a country our size.
CN-235 ... still a requirement as PAF only bought 4 from IPTN in 2004, of the original requirement for over 12. PAF did end up buying some used C-130s after that but the requirement is still there I am sure. I think we paid only $10M each for the basic transport versions while the VIP version was $25M or so ... while no C-130s, the extended CN-295 can carry more troops then a base C-130. It falls short on carrying equipment like helicopters, trucks, APCs etc due to the width/height of the body, but should its a good tactical transport for moving men and pallets.
C-130J ... too expensive at around $70M. Better off buying older H models and upgrading them with newer e
engines and cockpits. But if we can get some used J models in the years to come, would be a good bet.
Il-76/78 ... quite a large transporter, even though a bit dated. I think we don't have a need for more than a couple more to add to our 4 in service already. Ours were bought from Ukraine but badly need an update similar to C-130s avionics wise and newer more fuel efficient engines. Used ones are around $50M or so.
Other newer options include:
Embraer's KC-390 ... still too new and untested, around $50M each.
Airbus's A400 ... twice as expensive as a new C-130J at $140M ... def not worth it
China's Y-20 ... another strategic airlifter that is brand new and untested. Is probably over a $100M each and has weak engines. Smaller then C-17 but larger then Il-76.