While attacking Iran was a stupid decision, losing some MQ-9 Reaper drones by itself isn't unexpected or a real problem. The US military had already stopped procuring those drones years ago specifically because they aren't survivable against modern air defense systems. The ones already in inventory are a sunk cost so might as well get some use out of them. Calculating it as a $1.3B loss makes no sense from that perspective since they have to be replaced anyway.

This is not clear at all. The MMA program, which is the MQ9 replacement, is mostly the same mission set, but has a slightly lower per unit price tag and lower capability - there is a good chance that the MQ9B ends up being the MQ9 replacement.

Also, the US military is still procuring broadly similar drones, and will be for a while.

The lack of survivability is not the fault of the drone design. The design set it has is to have high unrefueled endurance, a medium payload capacity, and a reasonably low cost. The nature of technology means that to do so it is going to be relatively slow and have a large wingspan.

Additionally, they were lost in missions which require loitering in predictable patterns near known targets, in which they were shot down mostly by optically guided missiles. There is no indication that there is an alternative design that would be more survivable. The only hope is that there would be one that is significantly cheaper, but that is not obviously true.

So all in all, these are valuable losses. When they are replaced, they are very likely to be replaced by a substantially similar design at a significant fraction of the cost of acquisition.

I'm really no fan of the US MIC, but the MALE/HALE drones are actually a decent design. While they are more expensive than they should be, they are and have to be pretty big aircraft with sophisticated sensors, and so a decent chunk of the cost really is justified. Chinese/Russian/Iranian equivalents are broadly similar in design and cost 25-50% as much, which is about what you'd expect.

All in all, the attrition is not necessarily unexpected but it is a real problem, will have real and expensive consequences, and ultimately reflects a tactical failure in how this war was prosecuted which is a material factor in the current bad outcome. Many people really did think they would be able to survive enough to loiter around the missile cities as a backup in case they failed to be drstroyed, and that turned out to be wrong.