....I've been overthinking this answer for days. In fact, before I reveal my answer, I have a question for whomever reads this.
What do you count as a holy grail?
There's a difference between Holy grails and white whales. White whale would be rare and expensive items, but a holy grail would be a one off item that many people want, and may not even exist.... right?
Didn't mean to derail. This is a cool question.