Trend Tracker, Polished diamonds are usually worth significantly...

Trend Tracker, Polished diamonds are usually worth significantly more than the rough they came from (dependent on successful polishing).The risk is not just sales and price but also cutting/polishing risks.
Wastage or diamond Yield varies greatly dependent on mainly on the starting rough diamond characteristics (shape, inclusions, cracks).Yield may be as low as 5% on a poor stone to a max of around 70%, usually under 50% even for a gem quality stone. It also comes down to price as a round brilliant cut usually is worth more than fancy cut (pear, oval) so more may be polished away but achieve a higher price.
Offcuts are common to produce one or more smaller pieces but not always as there is risk every time a stone is cut, bruted, lasered or polished. That risk varies for each stone as some stones contain more stress or flaws than others.
There is a distinct collector market for large or Fancy coloured stones, though as can be seen by the 15ct Fancy Intense Orangey Pink it can take time. You need the right person to come along and say "I haven't got one of those!"Vivid colours and Flawless are the key features in collectable, flawless more so in whites. Usually pure Vivid Red, Pink, Blue and Green achieve the highest prices, secondary colours usually decrease the value, though there are exceptions.Hope that helps!