In all seriousness, do you think that's why these guest musicians appear on their albums?
Surely there are cases where it's a collaboration for the sake of the music, but yeah, my default assumption is that it's a marketing gimmick suggested/arranged/forced by the label (or band leader acting like label manager, in the case of Kamelot).
Labels certainly think such collaborations are financially important, because they're always prominently crowing about them in their press kits. Just see any Blabbermouth posting: ""Poetry for the Poisoned" features guest appearances by Simone Simons (EPICA), Gus G. (OZZY OSBOURNE, FIREWIND), Björn "Speed" Strid (SOILWORK) and Jon Oliva (SAVATAGE, JON OLIVA'S PAIN)."
If the label can't manage to swing an actual performer, then they'll go with the producer. "Produced by Andy Sneap (MEGADETH, ARCH ENEMY, STUCK MOJO)"
And failing even that, then they really dig for the bottom of the barrel: "Cover Art by Travis Smith (OPETH, NEVERMORE, SKINLAB)"
They might give half as many words to describing the actual music.
Note that in the mainstream world, the guest appearance is the bread and butter of the industry. The charts are dominated by songs such as:
SOME R&B SINGER: Some Song (feat. SOME RAPPER)
SOME RAPPER: Some Song (feat. SOME R&B SINGER)
I know this is a different world than that mainstream world, but you don't think that label mangers take ideas from that world? Any little trick that will get someone to listen to a band for the first time is something that any smart label manager will jump at.
I haven't followed Kamelot too closely lately, but they just don't strike me as a band really tied into the music scene for the music's sake. They aren't putting out split EPs with their favorite bands, doing odd little side projects, or running a boutique label with a roster filled by their musical friends.
And the collaborators don't necessarily have to be bigger than the main artist, they just have to draw in fans from different circles. Which Shagrath and Strid do perfectly. And I'm pretty sure "Ozzy's guitarist!!!" is bigger than Kamelot anyhow.
Later in the interview, Thomas was quite candid about his desire to grow Kamelot.
Yeah, so it all kind of fits together in my mind. And again, not that there's anything wrong with that. Kudos to him for trying to make a living while simultaneously putting out un-shitty music.
Neil