I'm in my 50s and I don't ever recall a time when B&W was cheaper than color for amateur use.
I was talking about still photography in the 60s, 70s and early 80s. Colour pics were at least double the amount to get processed. 126 cartridges were about double b/w rolls.
My brother had a b/w Polaroid camera in the 70s and, when he upgraded to colour, the packs of instant film were at least double the cost.
Early ink-jet printer cartridges in the 90s: b/w was always cheaper than colour, although they made a sudden switcheroo about ten years ago - and it's now seemingly cheaper to print out drafts in colour?