The cost calculations for weapon sizes is incorrect. According to p168 of the CRB, "Weapons are built to be easily held and used by both Small and Medium creatures. Weapons can be built for use by smaller creatures but generally cost twice as much (since they require special miniaturization technology). Weapons can also be built for use by larger creatures with no increase in price."
PCGen is halving the cost of Fine, Diminutive, and Tiny weapons, and doubling for every step above Medium.