Yes; a million a month does seem far too high. I don’t believe it. Even with 6 secret service agents, the cost of their room and board, plus incidentals should not cost that much. Anything over $50k a month sounds like far too much.
The cost as quoted seems much too high. I doubt there is air support. Maybe the initial costs were high (special van and other equipment), but the fixed costs (mostly labor) should not be too high. This sounds like disinformation.
It is a lot more than that. The article cites 22 positions and I suspect that is not everything. Sounds like round the clock 7 day a week security, undoubtedly plus armored SUV's and maybe government aircraft transportation.