I don't know if you ever got an answer to your question but I broke down said percentages as best as I could through trial and error and generating hundreads of results.
The actual range might be off 1~3% for each but it should nonetheless help you and other people out
% of base price - Item quality
0 - Destroyed
1~49 - Broken
50~60 - Inferior
61~70 - Very Cheap
71~82 - Cheap
83~99 - Low
100 - Standard (Base price)
101~120 - High
121~140 - Fine
141~160 - Very Fine
161~180 - Superior
181~200 - Exceptional
I don't remember seeing any results over 200% of base price.
Hope this helps. :D
