The opex of keeping a constellation that large in orbit, has not been proven to be cheaper than operating a ground based wireless network (and Starlinks opex is certainly more than a convention geosynchronous satellite system). Starlink operates with an assumption, that has not yet been proven to be true - that the cost per kg to launch something into LEO will go down as time goes on. If this prediction does not prove to be true, then it has no hope of making money, much less being self-sustaining.
Beyond this, the shorter lifetime of their sat fleet compared to a geosynchronous sat, means they must be replaced sooner, but its not obvious that the sats are significantly cheaper - this on top of the inherent launch costs, and the much much much larger fleet, implies that there may be a disconnect in pricing.
Starlink is a miracle for people with shitty or no cellular infrastructure. There are places in Australia that have exactly one cell tower for signal and they get 3G speeds at best. And if that tower has a fault, they'll be out of access for days or weeks.
$99 per month for Starlink is a no-brainer.