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.