Why do people buy sapphire potions for so expensive?

I kinda get why people buy sapphire potions..

Kinda

But why do people buy them for such expensive prices for like 100 sapphires and 50 Sapphires??

Just feels illogical that you're paying 50 sapphires for 10

It's like paying hundreds of dollars for a 5 dollar bill to give out

If the prices were equal or something like.

10 sapphires for a potion then that's understandable

But why is 50 the cheapest and why are people willing to pay for that?