$3 a month is well worth it for a lot of companies even with a thousand followers, there are so many other services that charge far more for much less in regards to public awareness. Elon is under no pressure, since he has a low interest loan from Morgan Stanley and he needs to fork over something like $20 billion in 10 years. That could easily get paid off in half the time with just the revenue Twitter makes already. And since it's a private company he can do as he pleases with no pressure from anyone else.