Objectively speaking, if the subjective enjoyment of your music is generally increased, then that's a net positive. So it at least depends on the target audience.
If the target audience is over 35 than chances are their wallets are fat but their ears are already shot. That won't stop them from blowing a lot of money on stuff that doesn't make a difference at all (either measurably or subjectively) but if it makes someone feel better they should be free to waste their money as they see fit.
Ha, yeah there's a lot of snake oil in the business.
However, there is definitely a difference in sound, however subtle to some, between most tube and solid state amplifiers when it comes to recording music, as musicians tend to try to draw out certain sounds that are a consequence of the design of the amplifier, whether by overdriving the input or exploiting analog flaws, etc.
Even when comparing just tube or solid state amps, there can be a lot of variance between them.
This doesn't really apply to consumer-grade amplifiers where the goal is perfect sound reproduction. A good tube amp and a good solid-state amp shouldn't sound different to an untrained ear. But amplifiers used in production often try to differentiate themselves in some way sonically.
What if I'm balancing an increase enjoyment from feeling I've got better sound against a decrease in enjoyment from feeling I've being taken for a fool by snake oil salesmen?