Not only are spellcasters (usually) more powerful than martial characters, but magic is what dictates power in the Pathfinder Roleplaying Game. As spellcasters already have magic, items that modify this magic, such as a bag of pearls of power, end up being significantly more cost effective than, say, a +3 sword.
As a result, just as spellcasters get more powerful exponentially, their equipment only hastens the rate at which they pull away from martial characters.
Though not a complete solution by any means, One Bling to Rule Them All: Glyphed Weapon Wrappings introduces glyph wrappings, a new magic item type that allows for the temporary editing of a weapon's special abilities.
How This Helps
You just found a +1 vorpal longsword! Sell it, right? Wrong! With a glyph wrapping, that weapon can be transformed into a +1 holy speed longsword for about one-third the market price of that longsword. Now, the player has a fun beatstick that can be quickswapped back into +1 a vorpal longsword should the fight demand vorpal for some reason. The martial character has more flexibility, the party saved 18,500 gp compared to selling the weapon in the store, and now there's more wealth to assign to something other than magic weapons.
Maybe, just maybe, there will be something left to buy something fun once the weapon golfbag is full up with wraps.