I'm playing a cleric in Descent into Avernus and we are, currently, 12th level. There are a plethora of useful spells on the cleric list but many of them require materials like, "diamonds worth 1000gp", "rare incense worth 400gp" etc...
I'm not sure if other people have played this campaign, but we haven't had the time or resources to acquire thousands of gp worth of diamonds.
Meanwhile, in another homebrew game, my wizard needed to buy a 5kgp chest for Leomand's Secret Chest and the GM just hand-waived it. "Oh yeah, there's a guy in town who makes those
The frustrating part is, many spells are gated behind seemingly arbitrary component costs that require the GM's benevolence/judgement to grant access to a big part of your class powers.
In one campaign, I feel frustrated and my choices are limited meanwhile, the party monk has access to all his abilities all the time. I see it makes sense in the context of the campaign, though. What use do devils have for piles of diamond dust?
On the other hand, the game where my Wizard had free access to unlimited resource (provided I had the cash, obviously), my character felt much more powerful. Sometimes, too powerful. Wizards are probably more dependent on GM grace given their need/ability to copy spells.
I can really see a DM saying, "I'm happy to give them access to one use of Greater Restoration per level" or "1 raise dead per campaign".
In the occasional game I run, I like to drop it as part of treasure but I don't try to be specific: "In this lab, you can scrounge 500gp worth of material components." then I let the player decide what they find.
As a GM, how do you dole out components and resources to your spellcasters? Do they have to quest for them? Are they readily available? Do you even think about that?