I have tried the cheaper shafts from a couple of manufacturers and I can tell you that with out a doubt I can see a differance in the flight of the arrow. Especially with fixed blade broadheads on the front.

It's not just the straightness that is affected with the cheaper shafts. The consistancy in the spine, weight tollerances within the dozen, wall thickness are all less tollerant in the cheaper shafts.

Buy the best shaft you can afford.