Pricing a custom made stained glass window or lamp is as unique as the design.
There is no formula to determine the amount of time involved.
Three components are key:

1)Complexity of the design (amount of individual pieces)
2)Type of cuts (straight/curved)
3)Type of Glass

If you have chosen one of my designs and want something similar I would be able to give you a fairly close estimate of the cost per square foot. Custom work is harder to estimate and is not “set in stone” until the final drawing is approved.