If it pans out, Starlink can disrupt a massive, $1 trillion/ year telecom market that is itself booming. Depending on how well they can productize long-term (miniature receivers embedded in laptops, tablets etc.) they stand to capture whole percentage points or even tenths of that market, giving Starlink itself a valuation in the trillions.
It's also an ultra-high moat business, a truly global monopoly. Once you have 12.000 sats in the sky amortized and own the only launch service capable of servicing them, you are impossible to budge.