I'm gonna agree to disagree on this.
There are several things that set them apart from "gas station" knives. for me.
The blade profile and handle profile are well thought out. The handle is comfortable. The heat treat is well done (I have owned a few gas station knives in my life, and used way more). I have had and used many gas station knives that the heat treat was bad, or the steel used in the blade was not even cuttlery quality.
In fact, I have had knives as expensive as $30 that turned out to be no better than pot metal in the blade. (those knives were not even purchased at a gas station).
The steel that Opinel uses is consistent. It is not going to be pot metal. It won't be rail road track. It is not going to be scrap metal. It won't be mystery stainless in capable of holding an edge.
The carbon steel holds an edge just fine. It is not a super steel. But it is a decent carbon. Easy to sharpen, and it stay sharp long enough to do work.
The stainless is better from my use. It is a very fine grained steel, and gets plenty sharp, and in my use, holds that edge longer than the carbon steel they use. (which I would prefer them to harden higher).
I have had gas station knives that would not, with any amount of work, take a decent edge, or hold one.
Opinel have well thought out geometry. The blade is thin, slices well, and cuts. I have many many knives that no mater how sharp I get the edge, won't ever cut as well as an Opinel. (My Busse, Swamprat, Cold Steel, and even my custom knives just don't have the same geometry).
I could build or commission a custom knife that would out cut Opinels, and hold an edge so much longer that it would be no contest. There are plenty of makers that design and make thin, high hardness, super steel knives that will cut days and days longer than an Opinel. But they are going to cost me way more. I don't hold that against customs. They just cost more. Opinels are super inexpensive. I don't hold the fact that they are not custom against them.
I have traditional knives (mostly GEC) that approach, equal, or even surpass the Opinel for geometry. Some of my blades are thin, and the 1095 holds a better edge than Opinel's carbon. I have one old Ranger that has very thin carbon blades that is just a nasty slicer. It is thinner than my Opinel. (if I could find the darned thing!). You can find a lot of classic knives that are the equal in the slicing department. But it is hard to find them for cheaper. My GEC are all $70 plus.
It is important to distinguish Cheap and Inexpensive. They are not the same. Mora's are inexpensive, but does that make them cheap? I would not consider them gas station knives. I have not seen them in a gas station, nor have I seen an Opinel (but I have seen them both in a camping/gear store).
I have seen Buck knives in a gas station.
I have to say, I have recent Buck knives I would absolutely consider cheap junk, not worthy of a gas station. (I have a recent manufacture/design Buck lock back that has the worst fit and finish, worst lock up, and worst overall finish of any knife I have handled or owned in decades and decades). It was roughly 4 times as much as my Opinels (though I bought a batch at $10 per knife, so I guess it is more like 3 times as expensive). The Buck was way more. Made in the US. Cuts much worse, and just feels awful in the hand. It is a cheap gas station knife, even though it was much much more expensive. I have inexpensive Chinese knives built so much better it is embarrassing.
Opinel are not race cars. They are not rocket ships. They are quaint, and pleasing to my hand and pocket. Light, and quirky, and sharp and very effective cutters.
Some one else mentioned that they were poor at whittling wood. I have to strongly disagree. Best folding knife I have ever used to make a pile of shavings.
Would be even better with more blade shape options like a warn-cliff (which they are cheap enough to take and grind into anyway!)