There's a feat in Races of the Dragon called "Extraordinary Trapsmith" (
http://www.realmshelps.net/cgi-bin/featbox.pl?feat=Extraordinary_Trapsmith) that reduces the cost and time required to craft traps by 25% (or 50% for kobolds). I think we can adapt this feat for tinkers:
Design-Build ExpertYou can save time and money constructing a clicker by overlapping it's design and crafting phases.
Prereq: Craft(clicker) 5, Knowledge(any tinker design category) 5
Benefit: When you determine the cost and the time required to create a clicker using one of your own designs, reduce the base price by 25%. Because some decisions are omitted from the design and instead made on the fly during construction, the optimum design cannot always be achieved; the DC of tinkering checks made to operate a clicker made in such a way is increased by 2.
Special: A tinker gnome who selects this feat can instead reduce the base price by 50% for determining raw materials and time required to create a clicker.