Goblin Slayer

[David75]

I might be wrong but I think I remember these scrolls are hard to find and are remains of past civilisation. Some people can decipher them, but no one can make them anymore.
GS found only 2 in all his years of goblin slay, when he visited lots of ancient ruins.
As other adventurers do not mess with goblins, it's possible they do not visit ruins and have even less chance to find scrolls.
These scrolls are extremely rare and their price is high for that reason.

GS had a pretty clever idea, for at least 2 reasons :
He wanted to kill that boss, probably because it was too goblin friendly.
The scroll probably can't teleport more than one person.

[Kraco]

GS had a pretty clever idea, for at least 2 reasons :
He wanted to kill that boss, probably because it was too goblin friendly.
The scroll probably can't teleport more than one person.

Let's make it just a single reason:
They would all be dead if he didn't kill the ogre with the scroll.

It's actually quite funny this scroll was a better weapon against a single extremely powerful opponent than multiple weaker ones. Multiple weaker ones obviously is Goblin Slayer's usual opponent selection. However, it was a last resort tool in any case, so in that sense it doesn't much matter if it's the best choice against goblins or not.