hmm. i don't know how it goes down where you are, but if he balanced your tires and did an alignment, then told you everything is fine, and it's not, he is liable. up here in Canada, if i as a mechanic do any suspension work, and the suspension fails, i'm liable. as in i could be charged with involuntary manslaughter and go to jail if you crashed and died. now that doesn't mean bust the law on him and sue, but it means that you should be able to take it to him and say, "you put on these new tires, balanced them, and did an alignment, handed me back the keys and said everything looks good, but the car wobbles over 50MPH. you missed something." dont be an ass about it, but be firm.
in reality, you shouldn't have to pay.