In 1971 I spent a lot of time in a Baton Rouge bikes hop that had a $300 Schwinn in it.The bike was EXTREMELY LIGHT. I didn't have the good sense to buy that bike, Heck a plain jane Varsity or Continental was about $150 back then, so paying $300 for a bike that was about 60% of their weight wasn't really that expensive.
Rather stupidly/cheaply I bought a *** KOLKOFF (W German) for $110.It weighed about 33 lbs-10 speed.One of the chainstays broke away from the bottom bracket one day.I found a welder and he managed to tack/melt/bubble it back on.
$575 seems a tiny bit high for 1975.Schwinns were always really expensive then, and they might have had some agreement with their dealers that prevented their dealers from discounting.

Yeah, I was really smart passing on that Schwinn and getting that *** Kolkoff !

Charlie