I've got to say... A TRULY GOOD BICYCLE and a bicycle you enjoy are two totally different things. You enjoyed your MGWard bike for $99, I enjoyed the $100 department store bikes I had when I was a kid (born 1989) but... Neither of them was a particularly good bicycle.
Most of those vintage Schwinns (I checked and $150 in 1980 is about $450 today) were perfectly good bikes but nothing TRULY special. Much like a $450 bike from a decent brand today is a perfectly good bicycle but nothing special. Lots of vintage models did cater to more enthusiastic riders and ran $300+. So... $900+ today. I paid that for my Cross Check (flat bar) and it's a very good bicycle, but again nothing TRULY special.
As someone stated in one of your previous threads, a high end bike then could easily run $1000+, so $3,000 today (he actually cited an $1,800 bike). Now we're getting into TRULY GOOD territory. I'd argue that the $1,500 I put in my Soma Grand Randonneur resulted in a TRULY GOOD bike (the wheels were the cheapest I could find but hey, you can't have everything). Hell, The bike that guy cited would give you about $1,500 left over after what I have in my Norther.
The point of all this is... Let's not confused a fun, rideable bike with a TRULY GOOD bike.