Interestingly, it's the opposite now - B&W tends to be more expensive because it has to be done by hand at most shops, while color development is done by machine.
i love instant cameras but they aren't really used for professional photography except as a novelty or as a specific artistic choice, and sx-70 isn't a particularly stable medium.
Professionals aren't developing at home unless they have a darkroom, which were fully capable of doing color negatives in the 1970s. If you can shove color into a self-developing mobile consumer device, a professional can have it done.
Somehow this needs to be about poor constrained do-it-yourself professionals?
You can process and print B&W yourself. Color needs to go to a lab.
The consumer "street" photography of the time was mostly Polaroids, or little tiny box cameras you had developed at a booth.
This has all to do with a feel, and It could be that it was mostly shot in color and converted to B&W. Or, the wonderful dynamic range of B&W could be the reason. That's fine, but it has nothing to do with lack of choice.
Could you please elaborate your thought process here? For example, are you claiming the author was using obsolete tech for one reason or another? Or making a pretentious artistic choice? Or do you think these were taken in an earlier period, then misatributed as being from the 1970s?
