Does buying a cheap pillow case counter the quality of a good pillow?

Looking for comfortable side, back, stomach, sleeping pillow/cases under $100 cnd.

Buying a cheap pillow case to cover a pricy pillow could be bothersome. If the pillow case irritates your skin, especially your face, you will not use the pillow.

Consider a Casper pillow. I really like mine, plus you can buy affordable yet quality pillow cases from them.

For me, I prefer a quality pillow and a quality case. I feel a difference the minute my head hits the pillow.
I bought mine at Macy’s several years ago. I do not recall the manufacturer of either. It is a process that is done my feel.

I wouldn’t want a cheap pillow case that pills (has those little balls of fabric) after each washing. It’s rough on your face. So I would invest in good pillows and good pillow cases. I have bamboo pillows that I’ve had for a few years that I really like.

No. Because they do different things.
A pillow is meant to support your head and neck while you sleep so you don’t wake up with pain. A quality pillow will do this even without a pillow case. The pillow’s performance is not altered/affected by the case which is just fabric.

Pillow cases are just meant to protect the pillow from dust, sweat, and the oils on your face because over time your pillow IS going yo absorb all those things and become a germ factory, so the pillow case just makes the pillow last longer before you need to replace it.
The quality of the fabric of a pillow case depends on your personal preferences/needs.
You could buy a $2 pillow case from Wal-Mart and be fine.
If you want a softer fabric that will last longer, look for a higher thread-count, and yes you will spend more money.
If you have allergies, a pillowcase made of bamboo fiber will make your life better.
If you are acne prone, you can try copper or silver infused pillowcases (expensive though)
If you have dry hair, silk pillowcases are wonderful.