I think what it boils down to (I'm not and never have been a season ticket holder) is this, the ticket price for any seat in Tiger Stadium (not sure about luxury boxes but any other seat) is the same 40, 50 or 70 bucks, generally speaking. The TAF can be as high as $135 per ticket per game (7 home games) for the 3 East and West sideline sections and one of the Tiger Terrace sections on the West. Even the lowest TAF (North and South end zones) are $30 /ticket/game.
That means it cost the season ticket holder, at minimum,somewhere around 43% in addition to the face value for most expensive tickets. I, for one, am willing to pay that to get tickets. Friends will usually forego the TAF but it would be a lot to ask of a stranger IMO.
As for the itemized savings, that equates to the percentage of the TAF for that game that is their personal income tax rate. Of course, I'm sure they report any amount over face on their income tax as income.