There is also the issue of how the product reaches the customers which is overwhelmingly still through the middle men which are the physical and online stores, which is also were additional factors of "enticed" purchases or returns can come into play.
For example Marvel could claim a comic, which for simplicity only had a single cover version, sold out (meaning additional copies have to be produced via reprints) with 200,000 issues.
But these might only have been the copies sold to the distributors. Perhaps of these only 5000 were directly purchased by readers/buyers, of the remaining 195,000, 50,000 to went Amazon, 45,000 to other online shops and 100,000 went to physical stores, of which 20,000 were international ones.
However after say 6 months of the 50,000 issues sold to Amazon only 10,000 were purchased by their actual customers and 30,000 send back to distributor, retaining only a backup of 10,000 for purchases over longer time.
Similar among the other online stores perhaps only 15,000 were actualy purchased in the first 6 months and these shops react similary sending 20,000 unsold issues back, only retaining 10,000 spread among them as backup.
And when it comes to the physical stores, we have to consider the constant presence of bulk purchase deals ala: "If you buy 20 issues of low value comic Y, you can get a 10% discount on high profile comic X" which are much more impactfull for them than the big online stores like Amazon. So of the 100,000 purchased by the stores, perhaps 40% of those were purchased via enticement.
Finaly the stores might have only been able to sell 40,000 of these issues, with 40,000 send back to the distributor after remaining unsold for 6 months, with 20,000 remaining either because of contracts with the distributers (hence complaints like: "We have comic X rotting on our shelves") or as actualy backup.
So of the proclaimed 200,000 issues sold, only 70,000 were actualy purchased by the customers themselves within the first 6 months after publishing and therefor actual reflective of the comics success with the audience. The remaining 130,000 then remain in limbo either with the stores or the distributor.
The distributers who had recieved them back might rebundle them with newer comics and/or decrease their prices and the shops might do the same, with the most important factor being to "empty the stores", because of the upkeep involved.
Likewise someone might put a comic in a best seller list, but that is only in comparison to how many issues were sold in comparison to other titles, but isn't necessarily reflective of the "dead stock" that remains after the initial sales burst.
International publishing and distribution of american super hero comics like those of Marvel and DC are another interesting factor to consider in terms of a comics success, because of the major presence of local publishing companies which produce their own stock, rather than being reliant of buying and shipping from US based distributors like once Diamond or now Penguine Random House.
For example in Europe a company called Panini Comics holds the license to publish both Marvel and DC comics alike, which outside the UK are translated into local languages and then printed on site. However Panini seldomly if ever publishes single issue floppies. Instead they primarily only produce trades paperback versions which however are also bought by regular bookshops.
This however also means that many satelite titles might never see publishing at all because the management of Panini comics might be more picky about which titles they will bother to have translated and published.
Some satelite titles might only ever see publishing in europe when their stories are tied to major events, which will result in their respective chapters being bundled with "core title" issues in trades.
While there are specialized shops in many european countries which sell untranslated single issue "floppies" they import directly from the US, the audience for these is obviously even smaller than that in the US, because of different mentalities and tastes.
Infact the majority of such shops tend to be "fantasy and sci-fi" stores which are much more diversified in their products. So the newest "floppies" imported directly from the US might only be present in a few boxes in a corner or sold directly from under the counter, while the rest of the store is reserved by shelves with regular sci-fi and fantasy literature, mangas, posters, RPG system handbooks and merchandise, collectibles, european comics and the Panini paperbacks of Marvel and DC comics.
So in terms of success a particular comic might potentialy only sell 10,000 floppies internationaly, but the issue itself might end up in a paperback which sells over 1 million volumes internationaly a few months later.