It's very difficult to give a figure for what to pay for a secondhand tool, because there are so many variables. Are you trawling the bootfairs for bargains, looking out on Ebay, or looking for one from one of the reputable secondhand dealers? Do you want good cosmetic condition, or just 'complete'? Are you prepared to buy several at rock-bottom prices in the hope that one will be a good 'un (or as doers-uppers), or do you just want to buy once and be done with it?
Another factor is the tool's function. It's a large lump, but intended for fairly precise work - truing up stock, jointing boards for table-tops, etc. So whilst a jack plane, used for fairly rough work, could tolerate a few minor faults and out-of-flatness of the sole, a try plane really needs to be better than that. The quality of the work you do for the next few years could be influenced by how good your try plane is. Is it worth cheese-paring on such a tool?
A brand new top quality try plane will cost £350 to £400, so arguably anything around half that or less for a secondhand try plane in very good condition is fair. If you can pick one up for less, so much the better. That said, setting a budget for any given tool has to be a purely personal decision.
There are a couple of things that might help. An 'advanced' search of Ebay for planes sold recently might show a trend in prices, and some of the dealers (there's a list of good dealers on Alf's website 'The Cornish Workshop') show their stock with prices on their websites. It's been suggested that Ebay prices vary a bit with the time of year, with dips during summer holidays and in the run-up to Christmas.
My personal view is that your try-plane is one of the workshop's foundations of accuracy, so I'd be prepared to spring about £100 to £125 or so for a really good example from a dealer or Ebay. If I managed to snaffle one for less, I'd consider I'd got a bargain. An alternative approach might be to look for one with a well-worn blade and snaffle it for as little as you can, then buy and fit a new blade and cap-iron.
Just one final point on testing it. Don't try checking the straightness of the sole with a 'straightedge' of unknown straightness. Try instead sharpening up the iron, then finding two longish pieces of wood - say about four feet long or so - and edge-joint them with the plane. If you can achieve a light-tight joint between the two pieces, the plane is doing what it should - the sole is flat enough for purpose.
) in perfect nick apart from the paint which only approx. 30% of the original was left. I remember I had no hesitation in paying that at the time.
