Hi spooner777,
I also use Cura so the material cost estimation is not the problem. And as you say, only material costs are veeeeery low, so I think the material estimation after slicing is precise enough. Even if later the filling has to be denser or similar, the material costs do not impact the overall price in a large amount.
On the other hand, if we charge something to somebody then we cannot charge him/her our problems (extruder jamming, failed starts, loosing time because of low print speeds at badly tuned printers etc.). So I guess it is only the material cost and the printer payoff. To payoff the printer we should know how many kilograms of PLA or ABS will our UM survive - 10, 100, 1000? Can anybody guess? Are there some durability tests made by the Ultimaker team to answer this question?
I see from your answer that you have the same problem with estimating the value of our printouts. I guess for the time being the fee it is "guessing" and waiting for the market to balance this issue out.
But anyway, you have made a first attempt. I have thought about five times the material costs, otherwise we get close to the shapeways and co. prices and I am not sure that we can compete with their printouts and materials.
Let's see if anybody else has any other ideas?