To directly answer your question.. "Would this be of value??" .. YES!
My comments here are based upon the fact that my models are $5-$10 in price range.. I realize that these ideas may not be reasonable for steel/glass/silver materials, and won't be appropriate for the folks with "more expensive" stuff. It would, however, be good for us "small parts" folks.
I personally don't expect these test prints at a drastically reduced cost, but I think it'd help if we could break apart minimum order and shipping from the cost of printing.
On many of my models, I would have been more than willing to pay even a little extra for test prints, given the following:
1) No minimum order (only print one)
2) Only available once - for models not previously printed (see "flag" below)
3) Expedited turnaround
4) Complete review/critique of any printing/cleaning problems from the production team
5) Some way to see a set of high-res photos of the printed item
6) By default, the item would NOT be shipped, but discarded
then:
7) Option to pay (separately - after printing) to have the item shipped (regardless of success or failure)
==========
At worst, my suggestion would be to add a "notes" field to the order/invoice process... there are many uses/reasons for this, but in this specific case, I could request "Please ship regardless of condition".
==========
Shapeways loses a bit of money when shipping multiple packages for the same order. If there were a way to request "Ship everything together", the amount they recoup on shipping might cover the cost of shipping (single) test prints.
==========
I
STRONGLY support the idea of a flag on each model that indicates "Has been printed successfully". This flag should be set by the production team, not the shopowner, and I would go so far as to only allow the shopowner to turn it off, not on. It should also automatically set back OFF if a new copy of the file is uploaded. Unfortunately, this may require a per-material flag.. a bit of work for SW web folks. <grin>
This would also serve a second purpose.. back to the production team.. so as to not have questions about the printability of an item that has previoiusly succeeded.
Personally, I would go so far as to include a count as to how many of a model have been sold to date... I realize that some people may not want that kind of info shown, but I would like it for my shop.
==========
As a dreamer, I wish that when I get the email "Your model has been shipped" that it would include one low-res picture of the actual model as it's being shipped. But, I fully realize that would be adding extra labor. <grin>