Buy a iphone case with $100, cheap or expensive?

All the case made by crystal, so cheap or expensive?

Not very expensive.
I ever brought a case from icolorcase.com, and they offer the same price.
But the quality is really great, so it is worth that.
If the one you brought is really with great quality, then the price is ok.
I also got 5% discount with this coupon "SPFYF5", so maybe you can try it next time.

It's about the right price for a cover.