I don't see the prices or indeed the value of the rarer vintage pieces falling back any time soon. Top condition highly desirable pieces are now mostly in the collections of enthusiasts and very few fresh examples come to market. Logically supply and demand continues to push the prices up.
I bought a DRSD for £18k two years back, I would struggle to find that same watch now for under £25k to £30k. At that time Red Subs were around the £9k mark and 1665 Great Whites were around the £7.5k mark, both have doubled in value and some in a little over two years.
I have just done exactly what you were suggesting, putting some serious money into a top drawer vintage piece, but the right watch doesn't come cheap or is easy to find and in this scenario it is better to buy from one of the world's top sellers rather than a lesser outfit.