I get occasional emails in my inbox from online dealers of second hand or pre-owned tools. I'm mainly interested in woodworking tools but these dealers also have tools from other crafts.
A couple of years ago (2015) the price of these were acceptable but due to the popularity driven by woodworkers to get hold of, for instance, old Stanley or Record hand tools the prices in the UK in 2017 are rocketing. A real case of supply and demand dictating the prices.
Now some of the lesser used tools are at the point of being the same or more than their modern day brand new premium tools like Lie Nielsen or Veritas (assuming that LN and LV are producing their version of those models). I recognise that dealers still have overheads to run their websites, have warehousing costs, wages to pay etc so they do have a mark up.
That's not to say there are no bargains left to pick up. There are other websites where individuals can still sell their grandfathers rusting #4s and old chisels for a few bucks. Craigslist and Preloved both spring to mind. eBay of course can be a nightmare as you have to bid against somebody else (unless it has a fixed Buy It Now price) and may end up paying more than you should.
So if you are in the market for relatively cheap pre-owned tools best to scour sites like the latter mentioned, yard sales or flea markets rather than going to a dealer.