The important thing is that the aircraft in question isn't going to be attacking something valuable today. Looked at another way, the attacker has still made an investment in fuel, warload, pilot flying time, airframe life, whatever in getting that plane out. These are assets that are gone and will have to be replaced. Now, the value relationship between real and virtual attrition is variable and depends on circumstances. As you point out, to the USAF, there is a world of difference, to the air defense system crews, there is almost none.
Virtual attrition can result from quite subtle interplays.
For example, the Iraqi SCUD missile attacks on Israel and Saudi during the Second Gulf War caused literally hundreds of aircraft sorties to be spent in chasing around looking for missile TELs rather than pounding on the Republican Guard. Those strikes that didn't happen were all virtual attrition attributable to the missile attacks. Virtual attrition doesn't even have to be caused by an airstrike being diverted or aborted. To do so, it needs a jamming pod. That takes up one hardpoint per aircraft.