As JackSimth points out, 36k of magic items is a lot and the loss of AC bonuses is particularly pronounced. For example, for the Barbarian:
+1 Flaming Greatsword (really, who fights with a morningstar?) (8k)
+2 Breastplate (5k)
+1 Deflection (2k)
+1 Natural Armor (2k)
+2 Resistance (4k)
+2 Con (4k)
+2 Str (4k)
+2 Dex (4k)
= 33k (3k left over for other items)
This gives:
+5 AC, +9 HP, +3 Fort/+3Ref/+2 Will, +2 attack, +5.5 dmg per hit,
Say that the Barb’s feats are Power Attack, Cleave, Great Cleave, and Weapon Focus. Barb is likely to have the following stats, in rage, with magic: Ability scores 24 Str (16 base + 4 rage +2 levels + 2 magic), 16 Dex (14 base + 2 magic), 16 Con (14 base + 2 magic).
HP: 112, AC 20 (+7 armor, +3 Dex, +1 Nat Armor, +1 Deflection -2 rage), Attack bonus +18/+13 (+9 base, +1 magic, +7 Strength, +1 Focus), Damage 2d6 + 10 Str + 1 magic + 1d6 Fire= 3d6 + 11.
If he has Power Attack/Cleave/Great Cleave, he can Power Attack for close to full and he’ll be very likely to kill a lion in one hit. Meanwhile, the Lions only hit him with primary attacks 40% of the time and they do pitiful damage. If all 12 Lions could Pounce on him at once (clearly not possible), he’d be in trouble. As it is, if he wins initiative he can probably charge a group of Lions and kill most of them. When the lions get to go only a handful of lions can attack him at once, and then he can Great Cleave them. This is just one character (admittedly one pretty well suited to fighting groups of low AC enemies).
Now think about what happens when his attack bonus is 2 points lower, his damage bonus is 5.5 points lower- all of a sudden he has to land two hits (with a little bit of power-attack) to kill a given lion. So there won’t be any Great-Cleave rounds where he kills four lions unless he rolls multiple criticals. His AC is now 15, which means that the Lions hit him 65% of the time, and so he’s taking over one and a half times the amount of damage he did before.
All this should indicate the extent to which character power at higher levels depends on magic items. Spellcasters can get away with fewer magic items because if relatively long-lasting buff spells exist, they can convert excess spells for the day into more useful things like AC, saves, and ability scores. Barbarians have no such option.