Some people are. SpaceX is private and carefully guards its financial information. Maybe it's pushing the limits with the Starship project, maybe it's not. Time will tell. The Falcon project is probably financially very successful. How long it can prop up Starship is unknown.
I'm pretty sure none of the people alleging SpaceX is a scam are trying to say anything as reasonable as that. Not least because that would be in no way a scam.
ETA: It's a conspiracy theory, plain and simple.
What is SpaceX allegedly lying about? Its prices? That's a logical impossibility. Is SpaceX lying to its customers about the service it provides? Obviously not; those payloads are going into orbit. Is SpaceX lying to the public about the viability of reusable rockets? Almost certainly not (though we do have to infer a couple things from the facts we are able to directly observe). Is it lying to the public about Starship? I don't see how. The Starship launches and their fates are public knowledge.
Is SpaceX lying to the SEC about whatever it is that corporations are supposed to tell the SEC? There's no evidence of that. Is it lying to the IRS? There's no evidence of that, either. Is it lying to its investors? There's no evidence of that, either.
It's all ad hom and connect-the-dots. And there aren't even any other dots. Just the ad hom. All the other dots connect us to the conclusion that SpaceX is not a scam.
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As for using SpaceX profits to prop up Starship: This kind of thing is a normal and healthy business practice. Besides which, the US government has a long history of using taxpayer money to prop up aerospace projects. Notably the Space Shuttle, which is notable for being a rare functional boondoggle. And of course ULA, which receives government subsidies to stay in business.
Besides those obviously problematic examples, there's also the much less objectionable practice of using NASA contracts to have taxpayers absorb much of the risk associated with aerospace R&D. NASA pays for the project, and the private aerospace industry reaps the benefits when the R&D pays off. Grumman fought hard for the Lunar Module contract, and used the techniques they developed there at the taxpayer's expense to develop the F-14 for the US Navy. Not that I'm complaining. I think American taxpayers got good value for their money, both from the NASA project and the military project. Just as I think taxpayers have gotten good value from the R&D contracts NASA has awarded to SpaceX.
Some people see it differently, though, and I can't figure out why. It's obviously not an evidence-based viewpoint.