I think the PC wealth guidelines are on of the best things since sliced bread. Keep in mind they are merely guidelines, but they make the CR system work and that saves the DM a lot of trouble.
BTW, the NPCs are supposed to have less wealth than PC. There is a guideline for NPCs and one for PCs.
The rules assume that PCs will fight monsters the majority of the time. Most monsters have squat for treasure. Killing an NPC brings in the money, but these are also expected to be savvy opponents.
If you increase the wealth of NPCs, it will do nothing to affect the relative wealth of PCs in the long run. A party of four PCs is likely to have killed at least 4 comparable level NPCs while making the journey from level n to level n+1. Increase the NPC wealth and you only accelerate the rate of acquisition for the PCs. Meaning you need to give the next NPCs yet more stuff to keep up...
If you want to slow down their accumulation of wealth, have them fight more monsters and more lower level mooks. The mooks may have wealth, but almost all of it will be sold for cash -- triggering a 50% liquidity tax (sale price is half market price).
As for the "few and precious" theory of magic items, it is a nice idea but it tends to hurt the PCs. Just be careful. The game as written assumes that PCs have access to emergency potions and scrolls. There are a lot of monsters that are extremely physically tough for their CR, but are quite easy to outmaneuver with a bit of magic, e.g. hydras.
It is also very harsh on some PCs if they do not have the opportunity to improve their saves with magic. That can really hurt their survivability. Do you want to play the Rogue or Wizard with a +5 Fort with the Evil One unleashes a Disintegrate with DC 21? If you limit the magic you also need to soften up the DCs.
