iOS 16.0.3 Still no toggle. My wifi connection is solid, i can make sandbox purchases without issue.

Yes, this is still an issue after updating to iOS 16.1

Also seeing this in a number of currencies e.g. UK price tier 60 is returning 99.99 instead of 89.99

Yes, i did get this working eventually, the missing piece of the puzzle for me was the sandbox test account needed to have 2FA authentication setup. the flow for doing this was a bit weird and very non-obvious, IIRC it involved trying to sign into a production Apple service with the sandbox account, confirming the email addresa nd adding a phone number and then logging back into the sandbox service. Hope this helps