The overall numbers of pilots lost are in fact even higher than those of gunners because early in the war only single seat Il-2s were in service and therefore only pilots were lost...
Even later in the war you will find that the number of gunners lost, is no more than about 1.5 per pilot lost...
Just check in the history of any soviet assault regiment, this thing about gunner losses is simply part of post-war myths (probably inspired by cold war propaganda or something like that...).
BTW, I myself read it time and again, and believed it for some time
(however incredible the difference may now seem (I mean : if these figures are to be believed about four men died for each Il-2 (1 or 2 crew) shot down, excluding prisonners and injureds, this is complete nonsense...), which just goes to show how much it is true that if you repeat something often enough it becomes true for most people, whatever the facts...