a 2012 is $1400 and a different bike than a 1984 520.
He isn't asking too much, the question is whether you want to spend $445($375+$70shipping) for a bike with 27" wheels and 126mm spacing when most stuff nowadays is 700c with 130-135mm spacing. It's not clear to me that those brakes can be adjusted to fit 700c. I've put 700x35mm wheels on long reach centerpulls that originally went on a bike with 27"x 1/4" tires and the handling was about the same. The other issue is whether you want a bike without a warranty.
It's a nice bike, a modern frame will be stiffer and better able to carry large amounts of weight but that would be a nice riding bike.

It looks like it would be a good learning experience.

I think of old bikes like that as something someone with more than one bike buys because they want THAT bike. If it was me and my budget was $500 come hell or high water I'd want to ride the bike, pick it up, see if the headset was good or notched, how true the wheels really are. Drop the chain off and see if the crank turns easily or is notched feeling or loose. If it can ride in a straight line without pulling to one side. If the bearings run smoothly. Stuff you take for granted with a new bike.