The cost model was built for one city. Presenting it to the Florida Local Government Information Systems Association across several conference years turned it into something other jurisdictions could use.
Chargeback in local government is unusually hard, and not for technical reasons. The agencies being charged are often independently governed, with their own budgets and their own elected leadership, so an allocation they consider unfair is not an internal dispute — it is a political one. The only defense is a basis that is measured rather than negotiated, published in advance, and applied identically to everyone including the department that owns the model.
What made the sessions worth attending was that the person presenting had to live with the answers. A vendor presenting a chargeback methodology has never had to explain to an elected officer why their allocation rose eleven percent.
Outcome
A method other jurisdictions could adopt, presented by the person who had to live with it rather than by a vendor selling it.