i would disagree with that...
I dont think album sales are generated by how "good" a band is. If that was true Britney Spears would only sell about 6 records and I can name a shitload of jazz albums that should've sold in the 100s of millions, that is, if record sales were generated by how "little or much" a band/artist sucks. But clearly thats not true, many talented artists don't sell well at all, and on the other hand many shitty artists sell way too many records. Record sales are based by whats popular, or what's "in" as well as marketing. Album sales have nothing to do with how good the album/band is, but more so how the single does on the radio. Does that mean a popular band is a good band? Not at all.
My point, just because Pearl Jam sells a lot of records does that mean they are a good band? Not at all