I can comment in a simple way as this;
Anyone who thinks Naval assets are example, one may also calculate the cost it in the other way;
via;
Deployment time (w Logistics) * Number of required units to have a presence at a location * Maintenance per-sortie * Sorties.
For a ship of FREMM size;
7-8 months * 1 * (1 + (0.5 ~ 0.3)) * 1 sorties
For a fighter jet + patrol aircraft wing;
1 Day (at most via refueling) * Multiples - 2 Patrol + 4 Wings of fighter jet * ( 1 + (0.2 ~ 0.5)) * 240
Or in simple terms, as often discussed among the environmentalist groups; ships are often blamed of having enormous amount of the emissions. In fact, ships provide the lowest emission per-tonnage carried compared to air or ground based transports although this doesn't mean ships are innocent on the emission but being the backbone of the shipping, they bear it.
Same analogy can be applied on her as well. Ships may seem to be expensive per unit, but you in fact it has more gains in unique ways and doesn't replace ASW- ASuW patrol or ASuW configured Fighter Jets 1 to 1 but fills a gap that can not be provided by other means in a cost effective way.