Vibration even after tire balancing

I have a 2006 Infiniti M35x (3.5 litre) with 31k on it that I lease. The lease is up in 3 months and I need to decide whether to buy it. At about 10, 00 miles I jumped a median (accidentally) that was about 6-8 inches at 50 mph. I had the alignment fixed and it seemed ok. The rotors went at about 13k. I replaced them. Then I started noticing a vibration without applying the brakes. The meineke guy said they could not balance the tires perfectly and recommended I get new ones. I procrastinated until 30k, living with the slight vibration, and then got them. I brought it back twice to have them balanced again and again. I still have a very slight vibration in the steering wheel at highway speed. I don't know the cost to replace bent wheels, axles etc. Or if this is even the problem. Any advice would be appreciated.