In some cases it might pay for itself in less than 1 month of service compared to the $/Mbps from the VSAT, using antenna hardware such as this and various vendors' choices of modems (and 3rd party VSAT ISPs that resell transponder kHz and operate teleports).
https://orbit-cs.com/maritime-satcom
Go price what it would cost for 1:1 dedicated monthly recurring billing to have 5 Mbps down x 1 Mbps up DIA service assigned to a medium sized maritime VSAT terminal that roams around the Gulf of Texas... Or even in a 5:1 or worse contended network.
What you'll see is the Iridium of course remains live and on the network and is used for critical voice calls and message and such, while the data network on the ship/offshore oil rig/whatever has a new better DIA path via starlink.
I wouldn't be surprised if equipment and certification costs would dwarf the actual fee charged per month and user in these applications, and the market entry barrier in such highly regulated industries is usually enormous. (It took Iridium a long time to get SOLAS-certified, for example; before that, Inmarsat was the only solution besides HF radio.)
In the market of providing fast, non-safety-critical internet access to remote places however, my guess is that Starlink is going to shake up things significantly.