Hi Erin,
Here's the scoop: yes, stockings vary widely in price and quality. Look at the photos above. This is the cost:
A. $55
B. $40
C. $30
D. $7
Here's a breakdown:
Photo A
These stockings are expensive because they're made entirely of silk. Now, silk is a heavier fabric than nylon so they cannot be as sheer as nylon stockings. On the other hand, although still fairly delicate, they're much sturdier than nylon stockings. Because they're made of silk, these stockings give a much more pronounced shine to your legs; they look like they wrap your legs in light. Because silk isn't a fabric with much "give," silk stockings don't stretch much; they hug your legs and thighs pretty tightly, a little bit like FF stockings (see below).
Photo B
These are referred to as "fully fashioned" stockings (often abbreviated FF). They call them "fully fashioned" because the stockings are fashioned, or shaped, like a leg during the manufacturing process. They're sewn flat (as opposed to around a tube, like stretchy nylon hose) and then "boarded," meaning they're fitted on a leg form and then submitted to heat in order to "set" the shape. These kinds of stockings, like the silk ones above, have very little "give" to them; they hug your legs tightly. They do this, again, because they're fashioned that way: rather than varying the tensile strength of the nylon mesh (as is done for stretchy stockings), manufacturers of FF stockings vary the quantity of fabric on a given stocking according to where the fit is to be had. More fabric in the upper thigh and the calf; less fabric at the ankle and the knee. By the way, the more dense are the filaments that make up the nylon mesh, the less sheer a stocking is (measured in deniers: 10 denier stockings are very sheer, 20 deniers less so, etc.)
Two common features of FF stockings are that you'll find a "finishing hole" in the welt (the dark band at the top of the stocking) and that they usually have a reinforced heel and toe (often abbreviated RHT). Don't be fooled by the seam; even cheap, run-of-the-mill stretchy stockings can have a seam. A sure sign that you have a pair of FF stockings on your hands (or legs, I guess) is that the welt is "folded over" (the seamstress uses the finishing hole to do this): the welt looks "doubled" instead of being just a darker shade of nylon or being an increase in the thickness of the mesh. When you put your thumb on the outside of the welt and your index on the inside of it and rub your two fingers together, it should feel as though you're rubbing two different stockings together.
You'll notice that the stockings in photo A don't have a RHT, whereas the ones in photos B, C, and D do. Again, silk is pretty strong so there's no real need (aside, perhaps, from an esthetic one) to have a RHT. Having said this, there's a huge difference between the stockings in B and the stockings in D (and, again, this is reflected in the price); the stockings in B ar fully fashioned with a reinforced heel and toe, whereas, clearly, the ones in D aren't. The stockings in photo D have no doubled welt, no finishing hole, and, despite the darker heel, no RHT. The darker heel is there just for esthetic reasons. You can tell, just by looking at the photo, that these are stretchy, basically one size fits all (yeah, right!) stockings.
A word on the shape of reinforced heels
There are four types of reinforced heels: Cuban, Havana, French, and Manhattan. You're likely to come across Cuban and French heels much more often than the other two. In the photo below, the three pairs of stockings on the left are Cuban-heeled, the two on the right, French-heeled (called, variously, "French," "French Point," or, simply "Point" heels). The difference between Cuban and French heels is obvious: in the Cuban heel, the reinforcement is "squared" whereas, in the French heel, the reinforcement tapers up into the seam. In Havana-heeled stockings (not pictured), the reinforcement is broader and somewhat more squat. In Manhattan heels (also not pictured), the reinforcement is "doubled" or "outlined" (in order to suggest or represent skyscrapers). By the way, as you probably already know, even pantyhose and tights can have Cuban or French heels.
Well, there you have it, Erin. I hope this helps some. The basics, again: quality stockings don't stretch much, they're fully fashioned (FF), they have a reinforced heel and toe (RHT), they have a finishing hole and a doubled welt. Everything else is dime-store stuff.
Love,
CJ