Why is the Porsche 911 SC so cheap?

In recent years the price of air-cooled 911s has soared, especially the 964 and the 993. Some now fetch £100k plus in the UK.

So why is the 1978 to 1983 'Super Carrera' so underrated? (Is that really what the SC stands for? Watch and find out).

Why can you still just about buy one for under £40,000? But how long will these bargain-basement Stuttgart classics stay cheap when people realise how awesome this underdog really is?