There is but one formula for pricing your stained glass artwork:
Worth to you < Price < Worth to customer

How much is it worth to you?
It depends if you want to get rid of it, or if you need to make a profit. If you don't need to make a profit, then any subjective value you ascribe to the piece as the minimum amount you'd need to receive as compensation to part with it, is the correct value. There is no formula for that.

If you need to make a profit, prepare to make some calculations. Keep in mind that even in selling the same piece with a $100 price tag, "Peter" might make a profit, while "Paul" would register a loss, because, for example, his rent might be higher.

The formula for "Actual Cost" is:
Materials + Labor + Fixed Costs + Opportunity Cost + Risk
  • Materials - You must calculate the cost of materials for a sample square foot of stained glass in the style and quality you intend to market.
  • Labor - You must calculate the amount of labor in that sample square foot for the going rate for a stained glass artist with your level of experience in your area.
  • Fixed Costs - These include the cost of your equipment, rental space, etc., amortized over the number of projects you expect to accomplish with these tools.
  • Opportunity Cost - That is the cost of not performing an alternate, and perhaps more lucrative activity. For instance, if you are a nuclear physicist with a wage of $100/hour, your opportunity cost of watching television is $100/hour.
  • Risk - If you make a stained glass piece that is not commissioned, but are taking the risk that some pieces may never be sold for their worth. The cost of unsold pieces must be factored in the price of every piece.

How much is your customer willing to pay?
This is the big unknown. It is quite possible that for a stained glass piece, or even all of your pieces, there is no price intersection with what it is worth to you, and what your customer is willing to pay. In such an instance, no sale is possible, and you cannot expect to craft stained glass panels and lampshades for profit. More often than not, the seller and buyer will agree to a suitable amount. Will it be at a profit, or at a loss? You increase your probability of making a profit by working efficiently and cheaply, while minimizing your overhead.

The formula for what your customer is willing to pay is:
Fashion Trend + Luxury Good + Topicality + Opportunity Cost + Utility
  • Fashion Trend - If stained glass is fashionable or not will impact on how much a customer is willing to pay.
  • Luxury Good - If stained glass is perceived as a luxury good, people will be willing to pay more. The recent influx of high-quality, cheap lampshades for China devalues the perceived worth of stained glass all around. Also, some types of glass will give off an impression of luxury at little expense, such as glue chip glass.
  • Topicality - People are attracted by representations of things they like and consider part of their individuality. For instance, horse breeders are likely to purchase a piece depicting a horse. Find popular topics.
  • Opportunity Cost - Customers make choices about what they purchase all the time. If they buy a stained glass piece, this must be weighed against another purchase they might also intend to make, such as a new sofa, roof repairs, or a restaurant meal. If the client decides to purchase a sofa, he might forego the stained glass.
  • Utility - When making a decision, the client will weigh the "utility" of a product against another. How much "utility" can be extracted from a stained glass panel, vs. a new lounge chair? Objectively speaking, a stained glass panel would have little "usefulness" compared to most products, though it might have some "utility" that cannot be measured conventionally.
The above is somewhat tongue-in-cheek; however, it is a combination of the common sense and basic economic principles behind every transaction.

The end of the formula?
There is no hard and fast rule to calculate the price of a stained glass window. There are too many variables - where you live, your reputation, your craftmanship, the rarity of your skills, the desirability of the end product, fads and fashions, gluts of Chinese imports - all of which contribute to the formula:
Worth to you < Price < Worth to customer

In other words, a sale occurs if the price is greater than the minimum price needed for you to part with your piece, and less than what the customer is willing to pay for it!