Amazon didn't exist at that time (or was probably still only selling books). Digi-Key still had a $25 minimum order. RS was pretty much the only game in town if you were a high schooler with a small allowance.

OTOH, some items were surprisingly cheap. A couple years after college, I had a small business running out of a spare bedroom making temperature monitors and there was a shielded audio cable with connector that I used for the sensor. Radio Shack's price was about $1.50 each but all the "real" parts houses were at least 5x that.

I don't buy a single anything from those others. I'm going to buy enough to meet their $40 minimum order. Shipping isn't free, and takes 4-6 weeks (remember this is 1960-1990). All this means that I'm planning all my projects months ahead to make a large order that will keep me busy several months (starting 2 months from now)

As an engineer my boss will approve $80 for a single resister after overnight shipping if that is what I need. The factory is buying the resisters a reel at a time (or similar large quantities)