There are too many uncertainties at this stage regarding delivery timescales and they do change by the month
Almost all manufacturers are struggling with this - VAG group have a lead time of almost 18 months on some cars so I don't doubt that Lexus is being fairly straightforward with their September 2023 delivery dates.
The RZ doesnt seem massively expensive to me in comparison to every other manufacturer. New car prices have gone a bit mental and it now costs over £30k to get into a decent VW Golf, and over £45k to get into a new C-Class. I understand there are a lot of comparisons against Skoda etc but thats like comparing a Renault to a Bentley. There are a lot of people on this forum who seem to focus on entirely numbers rather than anything else like build quality for example.