Details as follows. Please note, at the time when we went (Nov / Dec 2014), fuel was very expensive, around 108 rs / litre, but now it is almost 30 rs cheaper, so if you go now, your cost of fuel will be much lower)
The primary expense that anyone wishing to go on a similar road trip is going to be fuel and accommodation. Details of fuel consumed are as follows (accommodation will vary, according to travellers' preferences):
1st Fuelling:
Karachi
Approx. 51 litres
Cost: 4,850
2nd Fuelling:
Rahim Yar Khan
47.31 litres
Cost: 4,560
3rd Fuelling:
Lahore
41.09 litres
Cost: 3,899
4th Fuelling:
Islamabad
40 litres
Cost: 3,780
5th Fuelling:
Bhera (M2 interchange)
33 litres
Cost: 3,158
6th Fuelling:
Lahore
41.48
Cost: 3,900
7th Fuelling:
Rahim Yar Khan
39.2 litres
Cost: 3,399 (cheap because fuelling was done yesterday, after reduction in petrol price)
Total Fuel filled (a quarter tank was left when I reached Karachi): 293.08 litres
Total Cost of fuel: 27,546