Don't think I've spent more than $30-35 (usually less) for a fly line in years (except for a Teeny TS I wanted for some heavy saltwater stuff) and haven't had any problems. The Airflow WF6 I just replaced lasted 7 years and would have gone longer if I hadn't stepped on it so many times with studded boots. Only really bad line I've ever had was a Cortland Laser Line; absolute POS - stiff (wish my computer had that much memory) and worthless in cold water (possibly it was meant to be cast on an active lava flow?).
Keep your line clean (I like Glide) and it'll fly through the guides just like in the movies.
Regards,
Scott