Recently had two calls with an Iridium phone, one sent and one received, about 1 minute each. T-Mobile charged me $50 for those.
I found it very odd - it seemed like Iridium was somehow passing the call fees onto me, but I can't be sure because the T-Mobile rep I chatted with was unable to comprehend the situation (I suspect I was talking to an LLM, but it ultimately gave me a $30 rebate at least).
That usually makes Iridium -> terrestrial calls much more economical than the other way around, as telcos usually use the opportunity of terrestrial -> satcom calls to add on ridiculous margins. Conversely, satellite -> terrestrial calling is usually around a dollar per minute or less, these days.
In your situation, that would come out to a $50 (or maybe $25) charge per minute. Hefty, but that indeed seems to be at least in the ballpark of their listed rates (for prepaid here, for example: https://prepaid.t-mobile.com/connect/international-calling-r...).
It seems like cell carriers always charge more per minute for satellite calls than any satellite provider does, so I’m guessing they just set their rates conservatively to always make a profit on their end. And the demand for satellite calls seems like it would be pretty inelastic.