Surely the additional cost (as compared to sitting back at base on alert) is the fuel and maintenance cost of the machines incurred in those flying hours. Most costs (salaries, capital, insurance, crew licensing, etc) are unchanged by call-out v sitting drinking tea. Therefore be wary of "full cost" estimates when it is the "marginal cost" that was affected by decision to attend.
As the flight time here was short, I suspect that the answer is therefore "not much", even before you add the valuable training experience.
Posts above show very good reason why the alert / attendance was good cost / benefit call IMO.