As a young teenager my father gave me the job of setting up the keyboard in our new lock shop. A chalk line as used to snap horizontal and vertical lines on the big empty board. The result was over 1200 intersections where key hooks would be installed. It took several weeks but the board was finished with special key hooks holding 36 key blanks each. Several hooks were set aside for Yale Y1 and Schlage SC1 blanks but Kwikset was not very popular in those days at least in our area. Keyboard numbers were laid out according to Ilco numbers so it was easy to immediately find the key blank of choice if you knew the blank number.
Little did we know that 1200 hooks would not be sufficient to cover the 6000+ blanks offered by aftermarket key manufacturers today. Auxiliary keyboards were set up in other parts of the shop and new employees have a steep learning curve to learn where odd or newly introduced blanks are located.
Our family locksmith business is probably no different than yours. Most products in a lock shop have shelf life of infinity. Basic products such as mortise cylinders and key blanks have not changed in a hundred years. When a customer requires a duplicate Welch or Seger key, it is right on your board. If customer requires older lock parts or a mortise cylinder with an odd keyway, it is probably somewhere in your inventory. And if a customer brings in some new furniture key made in Asia you can probably find a Yamaha or Kawasaki key from the 1970s right on your keyboard which can be substituted.
Whenever a customer has an odd problem which you can solve, the first thing is to determine what the replacement cost will be to replenish your keyboard or inventory. While key blanks from years ago are still available, the demand is low and factory set-up cost is high. Keys which may have cost less than a dollar may now cost several dollars if they are available at all. Rumor has it the some blanks shown in key blank catalogs are ones which can be made but are not currently stocked by aftermarket key blank manufacturers.
When a customer requires an unusual blank or lock and you have it on the shelf, there are two possibilities. You can be happy to sell it at any cost just to get rid of old stuff. Or you can charge a fair price for a product which your customer cannot find elsewhere at any price. I suggest the latter.