Costly materials don't balance anything, which is why they are a bad idea.
The amount of character "wealth" - in terms of game mechanically affecting stuff such as tools, magical objects, and adventuring equipment is to the most important extent alloted to the party by the DM.
If the players expend some of that casting spells, the DM will have to make up for it in the placement of more equipment in treasure piles if he wants to maintain the game in the manner he was planning in terms of relative "wealth".
If the DM did not have a goal for party "wealth" - then any semblance of balance with regards to party "wealth" is a hillarious joke. And if the DM did have a goal for party "wealth" he's going to have to take costly material component expenditures into account.
In short, if the game is even attempting to be balanced in terms of equipment - the cost of the costly material components factors out of the equation - it simply gets added to expenditures and to income and never gets heard from again.
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However: why should we care anyway?
As things currently stand, characters get their money bins filled at level 9 when the Wizard gets Fabricate and the Cleric gets Plane Shift.
That's a stupid way for your monetary woes to go away, but why should they really be there at that point anyway?
You're a level 9 character. At this point, you've overcome approximately one hundred and four obstacles - any one of which could have been the major plot hook for a fairy story. Sooner or later, you're just going to marry the Princess and become the Prince.
And that level is ninth level. At ninth level you qualify for "Land Lord" - where you simply take a feat and arbitrarily become the Prince.
That doesn't kill adventuring possibilities. Prince Charming still adventures, he just doesn't stop in the middle of assaulting the Witch Queen's Black Tower to figure out how much the tapestries are worth on the black market.
Eventually you just need a motivation for adventuring other than "amassing money". Dragons should have enough gold to sleep on. Slaying even a halfling-sized dragon therefore should be netting you a tenth of a cubic meter of gold - or roughly two hundred and eighteen thousand, two hundred and ninety five gold pieces. You don't have to do that twice to not need more gold for anything other than bathing or sleeping on.
The only meaningful way to make people not strip-mine the worlds of imagination is to make them no longer care about money by the time they get there. When you get to the legendary adventures of 9th-16th level characters, there should be statues with ruby eyes the size of your head, bridges made entirely out of amethyst, and tremendous gateways made of high-quality bronze.
And if you are actually trying to screw people for individual gold pieces at that level, they will stop the adventure in order to strip all the jade out of the forgotten shrine, loot the golden flatware of the lycanthropic and insane lord of the valley, and pry all the moonstones out of the eyes of the statue garden of the chapel of silence.
Prince Charming doesn't do that because he is the Prince, and he already has arbitrary amounts of wealth. Unless player characters also get arbitrary wealth they will strip the scenery for cash.
"Gold Piece Value" just isn't a limiting factor to Legendary Characters. It can't be. If they for some reason needed cash - they'd just go get it.
And while there's a certain cache to playing "Scrooge McDuck" or "The Quest for More Money" - these are comedies for a reason. You just can't take a story seriously if the primary motivation is supposed to be cold hard cash once the character has already captured four dragon hordes.
If the story is going to even attempt at Drama instead of Comedy - character wealth must become abstracted at Legendary levels. It just doesn't work to try to worry about characters' budgets down to the gold piece at levels 9 and up.