Here is a '70s SG I saw a long time ago for sale.The previous owner had a '61 and a '73 and after the '61 suffered a malady he had the '61 parts changed over to a new '73 SG. Believe me when I say that no '73 SG has had a price tag so high.
There's a potential market for these things and I believe people are prepared to pay for them. Look at the hi-fi turntable market. Guys are making turntables and tonearms in very small numbers in tiny workshops and finding customers who are prepared to pay huge sums in some cases. Some of these items become very sought after even years after production ceases. Couldn't the same be said of the side to side trem? BTW I found mine amongst a load of second hand parts in a shop in Mitcham, S. London. Cost me £20 - a fair bit of money in the mid 70s. I didn't even have an SG to put it on! It now resides on my Custom and looks great.