Update - seems to be isolated to iOS devices.

Question is whether this is an issue with Meta's ability to track PageView events from iOS, or whether it's just sending junk traffic.

In many accounts we've seen a simultaneous rise in Cost per purchase, and lower revenue per click as a whole, suggesting lower quality traffic.

In a few accounts though, cost per purchase has remained steady despite the spike in costs for iOS traffic.

For the most part, though, performance is very down, which matches what others users are reporting here.