Lyceian Arcana, the sequel book, has rules for power components -- basically expensive items that are used up in the casting to increase the spell's power significantly.
Most of the spells in the core rules that require expensive material components are more powerful than other spells of the same level. The power components rules let you emulate a slightly weaker stoneskin (Abjure Nature 10/Gen 1 - DR 8/adamantine) when you're only 8th level, by spending 3300 gp, or to cast a resurrection spell (Heal Life 13/Gen 0) at 9th level, at the cost of 5200 gp. The thing is, these spells get expensive that way, so you'd rarely want to use power components except for very special circumstances. I know I sure as heck never liked having to give up 1000 gp to cast stoneskin. But the rules make it an option if you really want a one-shot powerful spell.
Requiring a cost for these spells can help you control the magic in your setting a bit. Resurrection and raise dead spells are expensive in the core rules, but in EOM they're mostly just restricted by how high their MP cost is.
