As far as the individual pieces, I believe the difficulty of the turning and the peculiarity of the wood plays a factor.
I can turn a bowl in far less time than it takes to complete a hollowform. Yet they could have the same amount of wood. Should they be priced the same?
Two different aspects are;
Working with your favorite, buttery smooth, even grained wood.
Compare that to a unique burl with voids and bark that you are trying to keep on.
It could be the same form but with these two examples two totally different prices.
Bottom lines for me are ...( Iknow your only supposed to have one bottom line but I'm special!)... Is it selling? Is it in the right market? Can I keep up with demand? Is there a demand?
Someone once suggested the dreaded word "Formula". The best one I have come accross for general situations is;
Height x Width x Skill level+Difficulty or unusual wood = Price
Since the third element is composed of two factors it can be where it gets tricky.
A 3" x 5" bowl by a novice turner [say a factor of 0], and from plain wood, [factor of 1 or 0], should be around $15.
The same piece with an experienced turner, [say factor of 3], and exotic burl [factor 2] = 3x5x5= $75
Why the two differences? The more experienced turner will
usually produce a more pleasing form,
usually have a smoother surface of wood and the finish will
usually be of a higher quality. The wood may have been bought for a price and it may have been more difficult to turn.
Just some food for thought.