One of the re-occurring questions on this forum is "What is it worth"? It's a difficult question for the newcomer (and possibly even the more experienced members?) .

Sheldon Brown started a rough price guide back in 1997 and while it hasn't been kept up to date, it has some good information especially with respect to the dynamics of price variability.
https://www.sheldonbrown.com/vrbn-a-f.html#pricing

[Edit: Michael Kone wrote the original article for and Sheldon Brown put it on the web]

There's also good data to be mined on eBay, but past auctions are only visible for a short time and prices can fluctuate with time of the year.

Searching the web, one can stumble on pages like the following one that has a list of used bikes with prices at which each sold back in 2000-2002.
https://www.pinionsandpedals.com/usedrb.htm

Another way of valuing is to look at the cost to build or get the same thing new, but this has no meaning when it comes to museum pieces. However, I think for the most part, a lot the bikes discussed here while perhaps collectible, are also ridden rather than framed.

Of course the perceived value can differ based on the perspective of the buyer versus the seller. When I sell, it's worth a lot. When I buy, it's not worth quite so much.

Anyhow, it seems a market is best at deciding the price. Is there anyway to look at older auctions on eBay? Or any general thoughts on price guidelines for used bicycles?

The fellow who worked up the guide that Sheldon references is in the process of updating it. I wouldn't expect to see it for a few more months though.

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Has there ever been consideration given to the idea of a "What's it worth" type thread here (as a sticky)? People could post photos, and other members could reply with either:

1) What they would personally pay for such an example if in the market; or

2) What they predict the fair-market-value would be.

I think it would be interesting, but I apologize if the idea is considered gauche or is somehow "against the rules..."

I suppose folks can always start a new thread with such inquiries, but more might participate if it was a group activity...

A significant amount of the postings here have to do with questioning value or the fun that results from mis-priced bikes ("catch of the day" / "numbskull"). A searchable database would be much nicer than a forever growing sticky thread, but that apparently has been good enough for other topics ("iso / trade", "classic rides"). Besides an appraisal thread, a collection of descriptions, selling prices, and dates sold would be very helpful. I'm thinking of routinely scraping some data from eBay, but that probably is against their user agreement.

The local markets are way to disparate for the typical run-of-the-mill bike to build an accurate database. In SF, you can get a lot more for any decent 10 speed in running confdition than most other places. In fact, CL is a better venue than eBay for the more common stuff. A mid level nondescript Japanese bike will fetch more here than in, say, Beaver, Oklahoma.

The only time vintage bike prices seem to even out across the country is for collectible or otherwise special or noteworthy bikes.

I think a database is a great idea but a huge undertaking. One thing I think you will find is a wide range of prices for the same thing. One day a NOS derailleur will go for $60 and the next week the eaxct same NOS derailleur will go for $90. Then, the seller does this every week, saturates the market and 4 weeks later and the derailleur now goes for $40.

It gets even more complicated with different levels of condition or with (it seems to me) very minor details that make an item "rare".

I enjoy watching prices on ebay and I bid on less than 0.1% of the items I watch. I tend to look at a particular region and era of bikes which comprises at most of 2% of the market. Also, at any one time, there is about 1000 items in US Vintage Parts alone. I like searching the UK and Italy sites and do some general worldwide searches. I skim Craigslist in Chicago/Madison/Milwaukee but have only been lucky with that once.

Again, a database would be very cool but very complicated. If someone wanted to set-up an Excel template, I would be happy to contribute the info I glean in my searches. What I don't know is if anyone else is interested in the stuff I watch.