Something not often mentioned is that having something you enjoy often leads to more playing time.
Regardless of the cost, if you have a cue that you thoroughly enjoy playing with (because of how it hits, feels, looks... whatever the reason), then you will usually want to play with it more. Playing more will typically improve your play.
Whenever I get a new cue that I'm excited about, my game tends to improve. However, this is probably more due to the fact that I'm playing more pool, than the actual performance characteristics of the cue.