It can vary so much. I got a 1982 Lotus Classique for $175. As far as purchases, it only needed new hoods, new cables and housing, and new tires. The hubs, headset, and bottom bracket needed repacking but the bearings, cones and cups were fine. I added a new chain, but the old one was not very worn.
OTOH, I also got a 1982 Lotus Supreme for $150 and spent at least twice that on all the bits I needed.
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"Don't take life so serious-it ain't nohow permanent."
"Everybody's gotta be somewhere." - Eccles