I wouldn't either, but thats just it Toyotas and Lexus might have slightly different design, but my god look at them. They're forgettable in most instances and ugly in others. However what I really take issue with is badge engineering. The Lexus LX570 is indentical to the Land Cruiser inside and out, and the LX570 is one of Lexus' most expensive vehicles. That isn't platform sharing, that is badge engineering. Platform sharing is the ES to Camry relationship.
That said my real issue with Lexus is that they don't look like anything, drive like anything (save the IS/IS-F) and they don't provide anything more (save the LS) that you can't find in a top of the line Toyota Camry or Avalon, especially when in comes to their SUVs. A Highlander is just as capable if not more so than a RX350. I could see if the Lexus had a different engine or better styling or something you can clearly see for the extra money the Lexus charges. Other than the dealership treatment, why would you buy an ES, RX, GX or LX?
The LS yes, it rides like no Toyota could and has things you can't get on a Toyota, plus its huge and is true luxury car (now), but it doesn't step away enough from the basic Toyota formula (dull, reliable, quiet, staid design) to excite me.
The SC430 could have, but it is worst car Lexus has from a competitive standpoint. Severly outdated and outclassed by every German convertible in its class. You'd be better off buying a Solara Convertible. The SC430 drives like a 2-door version of the previous LS430, hardly a GT or even "touring" car. Yes I've driven it more than a few times.
You can share platforms if each variant is different enough to stand on its own, and IMO most Lexus' aren't. The IS350, IS-F and LS are the only Lexus cars IMO that even make a dent in the German luxury car establishment. The LS is the sales leader here in the U.S. that does count, but it is priced thousands below the 2nd bestseller, the S-Class.
M