The problem is that there's a great deal of latitude in what a given amount of gp can buy you, in terms of effectiveness. This isn't so much of a problem if characters advance from low to high levels, since you can control (to some extent) what gear they find along the way. However, if they start at high levels and you don't place limits on what they can buy, they can become a lot more effective than would otherwise be the case.
For example, here are two sets of equipment, both worth 200,000 gp (excluding the mundane bits):
+5 keen holy longsword: 128,000
+5 fire resistance full plate: 64,000
+1 ring of protection: 2,000
gauntlets of ogre power (+2 strength): 4,000
+1 amulet of natural armour: 2,000
+3 shock flaming longsword: 50,000
+3 animated large shield: 25,000
+1 heavy fortification full plate: 36,000
winged boots: 12,000
heward's handy haversack: 2,000
+2 ring of protection: 8,000
+2 periapt of wisdom: 8,000
+6 belt of giant strength: 36,000
luckstone: 10,000
ring of jumping: 2,000
ring of counterspells: 4,000
+1 mighty composite longbow (+4 Str): 2,500
+2 cloak of resistance: 4,000
The bonuses with the latter loadout may seem low, but that's easily solved with magic vestment and/or greater magic weapon spells. The latter loadout is also going to be a lot more useful in a lot more situations than the former.
If you're finding this to be a problem, limiting what items the characters can start with is probably a better way to solve it. For example, you might say that only items worth more than X gp can be bought, excepting potions and scrolls (to limit characters scrounging as many piddly +1 items and utility items as possible). Or you might say no more than Y magic items per character. Etcetera.
