One explanation I heard on this issue from an ALPA national guy actually made sense.

Let's say there is a pilot who is married with four kids. He can't afford to put anything into the 401K because he is too busy trying to feed his family.

Then there's another pilot from the same company with the same income who is married with no kids. His wife makes a lot if money. He and his wife both max out their 401K plans.

The pilot who is struggling financially is subject to more dues than the pilot who effectively shelters a substantial amount of income from dues through the 401K plan.

I don't like paying more dues, but I believe that all income should be subject to dues not part of it. If ALPA needs the cash they will get it from you by raising the rate. At least this may have prevented a rate hike by evenly distributing the burden accross the entire pilot group.