sure.  when i can easily think of ten other 
things i'd rather do/buy with the cost of a cel, 
i'm going to pass.  (hmm... Nuriko cel, or down 
payment on a new car?)  

i think a less subjective measure is the cost of 
Hanken cels.  when standard cels from series 
creep up to Hanken-level prices, it's time to 
call it quits.