It's cost you approximately 10k for fuel, you might do 13~14 km/l on highway, further reducing the cost.
[TABLE="width: 455"]
<colgroup><col><col><col span="3"></colgroup><tbody>[TR]
[TD]Mileage (km/l)Consumption[/TD]
[TD="align: right"]11[/TD]
[TD="align: right"]12[/TD]
[TD="align: right"]13[/TD]
[TD="align: right"]14[/TD]
[/TR]
[TR]
[TD]Distance[/TD]
[TD="align: right"]900[/TD]
[TD="align: right"]900[/TD]
[TD="align: right"]900[/TD]
[TD="align: right"]900[/TD]
[/TR]
[TR]
[TD]petrol price[/TD]
[TD="align: right"]108[/TD]
[TD="align: right"]108[/TD]
[TD="align: right"]108[/TD]
[TD="align: right"]108[/TD]
[/TR]
[TR]
[TD]PKR/km[/TD]
[TD="align: right"]9.82[/TD]
[TD="align: right"]9.00[/TD]
[TD="align: right"]8.31[/TD]
[TD="align: right"]7.71[/TD]
[/TR]
[TR]
[TD]Total Cost[/TD]
[TD] 8,836[/TD]
[TD] 8,100[/TD]
[TD] 7,477[/TD]
[TD] 6,943[/TD]
[/TR]
</tbody>[/TABLE]
If you're 3 people, then it's more economical to take your own car. It'd directly subtract the cost of taxi etc in ISB/Muree.
IMO deciding factor should be the fun you'd have while travelling rather than going into detailed calculations. Additionally it'd be better to include Muree to Abbottabad route on your way back.