You are wrong, mostly. An slr w/o any electronic parts, no sensor, used to cost more than the basic ones do today. The difference wqs that the top dslr still didn’t carry much technology, besides the OPV and the shutter mechanism. It was, therefore, not much more expensive than the basic models. Think Nikkormat and Nikon F. As technology evolved, especially metering and AF, things started to get more complicated. Todays cameras use so much technology and the sensor/ADC system, which was then the film.
Think of how much you spent in film, film development, printing in those days, and you’ll see camera systems today are less expensive in the long run.
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.