Why do shoe insoles cost almost like a brand new pair of shoes?

I recently bought a pair of leather shoes for 70 bucks. The store offered me a thin insole for 7 bucks and I said, no thanks. After a few days, I felt uncomfortable walking in that shoe so I checked out a store for an insole. The nice lady had me try on one brand and it was gloriously soft! Then my jaw dropped when I heard the price was 40 bucks! What the?!

So I crossed the street to a BBB and checked out Dr. Scholls thinking, no way it would be near that price. Dead wrong was I. After going in two more stores, it’s clear an insole would cost me at least 40 bucks. But why??? Lol.