I'd say the level of "acceptable flaws" really depends on the buyer's intentions. Is the item going to be put on display or added to a collection, or is it going to be worn? Some vintage-loving folks focus on designer labels or perfect examples of this or that era or style. But others just like pretty dresses, and if flaws of one variety or another means we can actually AFFORD them, well, flaws it will be.
If only perfect items were sold, I couldn't afford to buy and wear most vintage! How sad. I don't have the funds to indulge in museum-quality garments, and furthermore, if you wear and launder something very rare and/or very old, you might be preoccupied with hurting it. But something that is already slightly "hurt" -- that would never make it into the collection of the "only perfect stuff" folks or the museum curators, those I could fix up to the best of my (or my seamstress') ability, and wear and enjoy without guilt or fear.
Lots of sellers specialize in "only perfect or near-perfect" items, or only "designer or high-end" items. Nothing wrong with that. And if that's your niche, then flaws should definitely be kept to a bare minimum. But there need to be some flawed things out there, so I have something to wear ; ). And I tend to sell flawed items when they are just too cute or pretty or interesting, because why toss aside something that, beyond a few "flaws," is marvelous?
Again, this is just my personal opinion. As they say, everybody's got one ; ).
p.s. Can't believe the seller wouldn't share the sell price. Not very friendly.