Okay, I’m confused by the last three panels. Is the punchline that the cobbler is just as deluded as the customer?
No, she’s being cynical. She knows it’s her expertise and not her virginity which is relevant.
I gather that if any gullible rich customers ask how she can continue quality cobbling even after losing her virginity, she can show them the empty bottle.
She says she knows cobbling skill comes from talent and practice, so her tale about it coming from her virginity is just a ploy, presumably to get customers to fuck her. It’s not clear however why she feels she has to buy a phony potion, unless it’s a cover for when a previous customer comes back and still finds her making great shoes for others.
It looks somewhat like people giving the most nominal possible adherence to absurd regulations. The apothecary frankly admits the potion is worthless; the cobbler frankly admits that she doesn’t much care. They’re both just going through the motions to product a (spurious!) “credibility.”
(I’ve known real-life people who do stuff like this with regard to actual regulations. One “minority-owned” business was owned, on paper, by the receptionist. She didn’t care; she got paid to sign the papers.)
These suggestions seem pretty contrived.
It seems more sensible that the cobbler, who’s mocking her customer for being dumb enough to believe virgins make better shoes, is herself dumb enough to believe a potion can restore virginity. That would be ironic anyway.
But that doesn’t hold up. If the cobbler doesn’t believe virginity is necessary - and she explicitly says she doesn’t - why pay for a potion to restore virginity? And why pay for a potion that both you and the seller are agreeing is fake?
Because the fake potion is for the benefit of her high-end customers. By purchasing it she doesn’t get caught out in a lie when they come investigating - it covers her tracks. It’s likely most of her customers don’t attempt to de-virginize her out of petty worry about the exclusive awesomeness of her shoes. On the occasions it does happen she has a ready made excuse for continuing to produce high quality goods.
Why use the virginity ploy in the first place? Marketing, marketing, marketing. “Well my boots were made by an enchanted cobbler who can only produce her wondrous works by staying virginal.” You can charge major bezants for that kind of exclusivity ;).
It’s called marketing.
You don’t really think she’s paying for a college education this way, do you?
Don’t forget the hot sexing, which is as a good a reason as any to do literally anyting in the Oglaf-verse.
The same reason you want to buy the best high heeled boots: vanity. The whole circle of materialism and life is all a scam and everyone pretty much knows it. She wants to call herself a virgin, so she buys a revirginization potion to fool herself, even though she knows it, and has done it before. Same with the “best boots”.
She’s not fooling herself. She knows the “revirginizing” potion is just sugar water.
She’s buying it to fool wealthy customers into thinking she’s still magically a virgin and thus can still produce the magically superior virgin-cobbler footwear, even if they happen to know that she’s already had sex.
The cobbler and the potioneer are laughing together at the idiot wealthy clients who fall for this magical marketing.
Except if it was as simple as that Kimstu, why would she even buy the potion? She could just tell the customers she’d had it.
Why lie about it when you can do it for real?
It’s like sales emphasising “ISO 9000” compliance. Doesn’t do a damn thing for the quality of the product, but helps sell to rubes. God forbid the rubes find out you’re not ACTUALLY ISO 9000 compliant.
In a magic universe with the possibility of truth spells?
…that for the most part work about as well as a potion of virginity restoration.
It’s debatable whether the cobbler actually has lost her virginity by the rules of the Oglafverse, anyway. Not to argue definitions for the real world, but canonically Navaan managed to keep her virginity throughout a lengthy session with The Apprentice that certainly included oral right up to a mouthful of cumsprite, and quite a bit more besides, and was all set to include anal as well; and none of it dumped either of them out of the enchanted city, which is how we know how the rules on technical virginity work (or worked there, anyway). I certainly can’t Google the page right here and now 
but regular readers should know the strip I mean.
But said session didn’t include digital vaginal penetration (as TA’s hands were shackled). So maybe fingering counts?
I guess it depends on what the meaning of “is” is.
Because you have to pay for a fake potion but lying about buying a potion is free.
And the cobbler is going to lie to her customers anyway. She’ll tell them her virginity is why her boots are high quality and, if your surmise is correct, she’ll tell them she restores her virginity with a potion. Both of these are lies.
So why not lie about buying the potion as well?
You are probably overthinking the narrative depth and consistency of the Oglafverse, but as Bryan Ekers pointed out, buying a “real” revirginizing potion means that she’s got an empty potion bottle as “proof” to show to clients who know about (some of) her “devirginizing” sexual activity.
Plus she can refer any unconvinced clients to the potioneer herself, who I’m sure has a great spiel about the magical complexity and powerful efficacy of the revirginizing potion.
Think about it: if you were trying to convince a rather dumb person that you’d been “cured” of some condition that is usually considered incurable but is physically impossible to detect with certainty, would you just tell them “Oh, I’ve been cured of that, trust me”?
Or would you show them your Fancy Official Medical Prescription and get the Fancy Official Medical Doctor who prescribed it to back up your claim?
Maybe. But again, TA ejaculated inside someone else’s body (just not her vagina) and that didn’t count.
Also maybe we’re overanalysing this, because it was quite funny as it stood.