I sure that headlamps were tried before. One of the first Duchess of Sutherland locos in the late 70s. It was quickly dropped.
Is the black 5 and turbomotive an example of us not learning from past mistakes?
With respect to bargains fairly recently I obtained 13 mks (1 Bsk, 2 cks and the rest SOs and SKs) for150.00. I've been fortunate with other bargains.
The second hand market remains boyant. Toy fairs, dealers and eBay. Some dealers are desperate to shift stock.