Wow, I haven't looked in for a day or so and then I see this fast moving thread.
I bought my 3.5i, to replace an Alfa I bought from new, this was a 2nd car, only considered changing it when a Cayman S came on the radar, 3yrs old, it met my budget as I couldn't justify buying a new one, during this the Z4 came into the reckoning.
I did all of the usual Pistonheads classifieds, Autotrader, BMW UK used and RAC. Knowing I wanted a 3.5i or 3.5is I came across mine courtesy of Autotrader.
On some of the searches I kept seeing Z4's at a much lower price than the 3.5i I had in mind, then I realised they were not 3.5i's. These cars were/are still commanding a much higher price. I also saw my local BMW dealer had some E89's out on their forecourt last week, none when I was looking 2 months back, again much lower prices, a quick check and they were 2.0s.
I'm happy with my car, but I recognise not everyone can go that far.
So some of the smaller engined Z4's must represent a bargain to some. ETTO.