When you buy a telescope eyepiece do you always have to spend more for better quality?

It depends what you want. For example, the Baader Orthos are in my opinion the best eyepieces around for planetary work and are not too expensive - middle of the road in fact. However they have comparatively narrow fields of view making them less suitable for deep space objects. Where it seems you really do pay is the "I want it all" eyepieces - wide flat fields of view, good contrast, minimal distortion etc etc. Things are much better if you are willing to accept you need different eyepieces for different occasions.