alt Hacker NewsOne lamp featured was a "mini Tizio". I bought the full-size one many, many years ago. (E.g. uses a Halogen bulb.) This article prompted me to think... So I just Goolged it. My vintage Tizio is now selling for about $1,200. (Cannot remember what I spent, but very likely my <$150 filter kicked in when buying.) So if you like these lights, maybe consider the cost an investment. If after a few decades you may want to sell, and you might do well. Note: My Tizio is not for sale as it is a superb desk lamp.
Alas, a good-condition Tizio usually sells for around $200-$350 used, depending on the exact model. First-generation models may go a little higher, like $500-$600. I bought mine a couple of years ago for about €250.
If you browse sites like 1stdibs or Pamono, you're going to see dramatically inflated prices, but I don't see why anyone would ever buy there. Ebay, Selency, Vntg, etc. are more likely to sell at actual market prices.