reply to u/EquivalentHead3589 at https://www.reddit.com/r/typewriters/comments/1cbzx1n/how_do_you_price_typewriters/

The primary difference is that listing prices don't indicate actual value. That is only determined by actual sales price. Things are worse for the listings which don't indicate much about condition as you're probably more likely to need to have the machine serviced and/or replace or recondition parts. This can often add a few hundred dollars (or significant research and time, tools, and elbow grease) to the bottom line to be able to use a machine.

I do recall a burgundy Olympia SM3 which sold in the last 4 months for right at $300 which was regularly used (loved) and serviced and in excellent condition with some fantastic photos. If you compare it to this Burgundy/Gray machine (https://www.ebay.com/itm/404901285037) for $299, but which has a missing key cap, and a damaged case, and may likely have other hiding issues. If you consider that you'll likely need to put a minimum of another $100 into this to get it up to the fighting shape that the first was in and it's still got damage, you'll start seeing the stark difference. The people with listings at $550-800 know they're not selling and they're just sitting there, so why not email them and ask more specific questions about condition and get a typed typeface sample of all the keys. Then make an offer for $200 +/- with some wiggle room for service costs once you've gotten it to see if they'll sell?

As an example, look at https://www.ebay.com/itm/226016437104 which is a Gray SM3 originally listed for $549 and now on sale for $428. The seller knows it's not moving. They state that they got it at an estate sale (probably for around $25) and they definitely did no work other than quick check of the keys. If you demonstrate that you've savvy enough to know the specific machine (what shape are the rubber washers on the frame next to the feet to prevent the carriage from rubbing against the frame? how what is the durometer measurement on (how hard is) the platen?), the market (in top shape maybe $300), and what servicing/repair costs are, they'd probably accept an offer of $150-200 and you're off to the races and they've made a solid profit.

The biggest issue in the typewriter market at present is the broad lack of information and knowledge about them on both the buyer and seller side. If you can demonstrate you've got more knowledge than the other side, you'll be in a far better position to negotiate, otherwise a seller can sit and wait an undetermined amount of time waiting for a sucker who will likely never show up.