I got 7 tickets on my way to Islamabad from Lahore and 6 tickets on my way back to Lahore.
But it wasn't anything like you mentioned. If its less than 160 km/h you get ticket of Rs.750 and if its above 160 km/h its 1500.
I got total 8 tickets of Rs. 750 and 5 tickets of Rs. 1500
Maybe its changed now, as previously they used to stamp the toll card, now they collect money on the spot.