The value of classic cars? Collectables whether cars or paintings or pottery are driven both by fashion and by economic circumstances. The fashion bit is the most dangerous because rather less exclusive items get carried up with the really rare items until the market changes. So whilst the Mona Lisa will never ever fall much in value, lesser paintings definitely drift in and out of fashion and up and down on price.
Its the same with cars. I know a lot more about Ferrari prices than Morgans and I have certainly seen prices of the more volume models like the 328, 348, 355 go up, then down , then up again and currently are drifting down. 328s have been on offer at 20k then up to 80/100k and back down to 60k and falling. A 250 California is a different issue altogether.
The interesting one to watch will be the E type, which has rocketed up with sales as high as 180k but falling now. I didnt want one when new and I dont want one now.
But what does it matter? I've just paid silly money definitely too much for a 360 manual spider, the last of the analogue cars. It will fall sharply from here but at 74 I dont have the option of waiting to buy at the bottom. If did that ( and assuming I last long enough) I likely wouldnt be able to get in a low 2 seater.