It it this designer's belief that no spell should REQUIRE a material component. If a spell is so powerful that a 5,000 gp diamond must be consumed to complete the spell, then the spell is too powerful for the level.
It's not complicated math.
Material components, while adding flavor to the game, need to go.
However, PCs that actually take time to develop clever material components for their spells should be rewarded with interesting effects... right?
And here's how my system works. Any PC may use material components to enhance a spell, generating a metamagic effect. By using 1 gp worth of components per spell level and taking an additional action (on 1 action casting time spells) to cast the spell, the caster is rewarded with a free 1 level Metamagic Feat "boost." That means, anyone using a 1 gp banana (that is consumed in casting) to cast burning hands, spends 2 actions casting the spell and gains an enlarged burning hands in return.
Therefore, a 3 gp banana (and 2 actions) are required to cast an enlarged fireball in this manner.
Since a 1 level Metamagic Feat isn't game breaking, the gp cost is nominal, but the time spent in preperation of the spell is not. In fact, during this time the caster is susceptible to attack and everything else, just as though he/she were casting any other full-round or multi-action spell. However, the DM may want to impose that more THEMATIC compoents be used in casting.
For instance, sulpher may be a more appropriate component than a banana in the above fireball.
Since this designer doesn't think metamagic feats are nearly as powerful (or interesting) as other feats in the game, the caster need not HAVE the feat in order to generate the desired effect. He/she only needs to spend the required amount of time and gp in order to generate the desired result.
The chart is not arithmatic, but exponential. To determine how much additional time and gp is required, square the "level increase" of the metamagic feat. Any caster generating a "free" 2 level boost must spend 4 additional actions and 4 gp per level to get the same benefit.
Obviously, the gp cost does not go up nearly as quickly at higher levels as the time spent to cast the spell.
A maximized fireball (3 level booze) would require 9 additional actions and a 27 gp apple.
But, this system is completely optional, and as you'll see in the following chapters changes with each college of magic anyway.
But, for the record, I am pro Eschew Materials for free for those DMs that hate this new system, but also hate Material Components.