If you are using new bikes then you may not face any problem on steep turns. If bike's engine is weak then you will have to drop one person to climb easily in some steep turns.
According to your plan till Deosai, total cost you mentioned is much. It will be maximum 10000 each because you are traveling in August and august considers as off season.
Its all secure to visit. As for road conditions: till Lulusar lake road is fine. after that its under construction till Babusar Top. From KKH till Chillum road is manageable but narrow road. From Chillum a few kilometers are ok but after that till Bara Pani no road but dirt track and if there is rain then dirt track becomes mud track. In August I hope you will see rental camps at three spots: 1: Sheosar Lake, 2: A few kilometers after Sheosar lake, 3: At Bara pani.
I think you should extend the days. According to my experience you need at least 3 to 4 days to travel till Deosai from Lahore.
I hope you have seen my thread, if not then check this link to get idea of the road conditions.
Feel free to ask question if you have any...