The Diamond-Tip Arrow is extremely rare, but it holds a very distinctive place in trick arrow history. Green Arrow used the trick to rescue the JLA in the issue where he joined the team, Justice League of America #4 (1961). The JLA were trapped inside a diamond that could have ruined Earth’s economy. (For some reason, diamond was very easy to come by in the Golden Age. This one was created by an alien to trap the team.)
Naturally, Green Arrow was prepared for just such an emergency. His Diamond-Tip Arrow was the only thing that he (or the alien that created it) had that even had a chance of breaking the nigh indestructible cage. He drew forth the most expensive trick arrow that had ever been created. Even taking into account the supposed expense of the super high tech arrows that he and Hawkeye would use later, this one was extravagant.
Going by the size of the diamond in the original appearance, it would cost an estimated $2.3-4.5 million on the low end. The biggest problem is simply finding a diamond that large in the first place, a nearly impossible task. (Again, in the Golden Age they seemed to be very abundant.) Due to their incredible rarity, it would make more sense to use an artificially created stone. Even at its lowest possible grade, a diamond that size would cost $900k-1.1 million. A quiver full of them would tax even Oliver Queen’s budget, and he was a billionaire.
This issue was addressed in the arrow’s next great moment, as the object of “The Archer’s Quest” (Green Arrow vol. 3 #16-21, 2002-2003). In this story arc, a recently resurrected Oliver Queen goes on a hunt for the missing arrow; he wants to use it on an engagement ring for Black Canary. During the quest, he reveals to Red Arrow (nee Speedy) that he only ever created one of these trick arrows, and that it was not nearly as large as the cover of that comic would indicate. “Artist’s rendition. They always exaggerate.” However, that single arrow cost more than the Arrowcar (a Batmobile style super car).