Well, if you have already collected many good cels from 
your favorite series, it's simply hard for you to buy more.
On the other hand, if you have no cel from your favorite
series, of course, you'll want to buy the cels whether they
are in best quality or not.  Like several years ago, 
Fushigi Yuugi cels are kinda rare, even the low quality cels
are very expensive and they sold out quickly.  But nowaday,
most fans don't seem to care about it anymore because there
are too many floating around in the market now, plus they're
getting cheaper and better quality too.