The purity of an Essential oil is the most important characteristic. An Essential oil that is not pure means you are putting additives into and on your body that may cause irritation, have adverse effects or even sickness. I know; there are heaps of cheap oils out there floating all over the internet.
"Pure Essential Oils?" How can they be pure when they have additives. If something is pure... then its pure! No discussion.
The CPTG ( Certified Pure Therapeutic Grade) certifies that there are no fillers, synthetic ingredients or harmful contaminants that would reduce their efficacy. Some essential oil suppliers such as doTERRA even put all their products and packaging through stringent tests to ensure a long and effective shelf life.
So in short, yes Essential oil prices vary hugely. Just remember ..
"You cant buy a thoroughbred with a thrupence!"
( yeah I'm old and remember thrupences..( 3 cents about)