The current incarnation of Iridium bought the constellation for only $35 million, effectively discharging the massive debt and allowing them to profitably operate the satellites without having to pay back what it cost to put them up in the first place.

Come forward to today and satellites are cheaper and more capable, demand for communications is higher, and launch services are much cheaper, so Iridium thinks they'll be able to put up a next generation constellation without repeating their history. It looks like they're planning on spending about $2.1 billion to build the satellites and $800 million to launch them, which puts the new constellation at about one third the cost of the original taking inflation into account, while being vastly more capable. (The current Iridium system gets you a connection which provides either a single voice line or 2.4kbps (!) data service. The next generation will go up to 1.5Mbps.)

Iridium is a fascinating story of hubris, spectacular failure, and eventual success.

Unrelated fun fact, an Iridium satellite was involved in the first accidental collision of two satellites. Iridium 33 collided with the defunct Kosmos-2251 in 2009. The relative speed was over 26,000MPH and sprayed a bunch of debris around the two orbits. Iridium has spares in orbit, so they were able to patch up the constellation without much trouble.