The costs of three models of helicopters are shown here. Find the weighted mean of the costs of the models.
$$\begin{array}{lcc}{\text { Model }} & {\text { Number sold }} & {\text { Cost }} \\ \hline \text { Sunscraper } & {9} & {\$ 427,000} \\ {\text { Skycoaster }} & {6} & {365,000} \\ {\text { High-flyer }} & {12} & {725,000}\end{array}$$