lol - the price. That's it. I've had some premium juices (+20.00 for a 30 ml) that were great, some that were awful. Flipside, I've vaped some non-premium e-juices that were under $10.00 for a 30 ml that are STILL in my e-
juice rotation (and they're staying there!) and some that were terrible, too.
You can't tell what's good or not so good simply based on the price. You just can't.