I heard often editors say that the numbers we get from the unofficial sales chart are not to be taken seriously because are far away to be close to the real ones. While many indipendent authors say that generally the gap is around 10-15%. Then anytime a publisher announces a big success revealing its number (ie. latest Amazing Spider-Man 1) the difference between the official number and the sales charts one is around 10-15%. Who we should believe? :)
sentenze

brevoortformspring:

You’re assuming a consistency where there is no consistency. Much like the earlier discussion of Marvel Time, there is no instant conversion of sales information, no magic multiplier that you can apply in all instances that will get you a correct result. Even the numbers quoted for AMAZING SPIDER-MAN #1 are an estimate, a rounding off, and they don’t include things like digital, or collections sales, or so forth.

I know you want to be an insider with all of the sales data, and use that to bolster your arguments for whatever characters and creators and story directions you like, but the fact of the matter is that you are no such thing. You do not have accurate sales data, and you are not privy to the publishing strategy of the Marvel Comics Group. And none of that, really, helps your argument anyway, because anybody that you’d be arguing to using those numbers knows this—at least anybody in a position to influence  what you want influenced.

I tally our numbers by a very simple metric: I count the money. You can feel pretty confident that I know what I’m talking about in this regard.