Perhaps there is a work around for Reality Revision if a Cognizance Crystal can be used as the material component (see linked question) as Craft Cognizance Crystal allows the use of 12,500 gp of "raw materials" to create a 25,000gp crystal over 25 days of crafting. "Raw materials" have no meaningful rarity so it's just a matter of having the funds. All good there... maybe.
So, now to Wish... a diamond is specifically cited as the expensive material component. It's not diamonds plural, it is a single diamond. The most expensive diamond you can find in treasure is worth 5,000 gp. A 25,000 gp diamond is so rare it doesn't even warrant a mention in random treasure tables.
To put the rarity in focus, even in a metropolis there is only a 75% chance of finding a magic item of up to 16,000 gp value. The maximum spell level for a metropolis is 8th, so no wish casting even in the biggest population centres listed.
How does someone procure one of these unmentionably rare 25,000 gp diamonds? And if using it for a Wish spell destroys it, how are there any left in a world with any wish casters in it?
It isn't a feasible material component when it is so specific!
The wizard has clawed his/her way up 17 levels, scrimped 25,000 gp, and then is blocked by the rarity of the material component.
Sure, make it cost a lot, but let it be practical to source the materials without becoming BFFs with Dumathoin (or whatever god of gems your setting has handy).