I dont think the price should exceed 5/5.5 million for what youre looking for, but I think the petrol (L/i) versions are usually cheaper in the Pak used luxury car market because HOBC is much more expensive than diesel and availability is also a key issue. Also, while people complain of low-quality diesel for BMW diesel engines, people also complain about low-quality, low-octane HOBC.
My recommendation is hence a 730d or 730Ld (est.5.0M PKR) but if you want more power, dont opt for a 730i 3.0L V6, rather a 740, 745 or something as such. I once (in 2009) saw a green BMW 745Li model 2004 being offered for sale on PakWheels for 38 lakh rupees. I believe this was in Islamabad, it had about 80k km, seemed to be in good shape and probably low priced because of very low demand for petrol variants of such vehicles because operating cost is VERY high.
Best of luck anyway