Douk-Douks are indeed pretty neat. Extremely slim due to the sheet-metal handles, and very easily made razor-sharp because of the soft carbon steel.
I also got a couple Okapis (formerly German-made for the African colonies, but now South African made) in the mail from Ragnar today, and quite pleased overall. The handles are a bit crude (basically like Opinel handles), but the backspring is both primitive and durable. The largest sizes are lockback, but the little ones I got get by with just the strong backspring, same as Douks.
The other traditional knife not mentioned yet is the Mercator K55K. Also extremely thin with sheet-metal handles, but a true lockback. I believe they're making them in shorter, more pocketable sizes these days. I'm not totally clear on what's happened to Mercator, but I think they're part of Otter-Messer knives these days.
Opinel, Douk-Douk, Okapi, and Mercator are, in my mind, a certain class of traditional Euro pocketknives I rather like, and all $20 or less on a good day (far less for an Opinel). The Asian equivalent would be the Japanese
higonokami friction folder. I need to pick one of those up one of these days...
I totally agree on the junk bin comment as well.
Most old knives at my local pawnshops are horribly marked-up, but I did get a whole box of knives, including a Case, a bunch of cheaper ones like Providence, two Schrades, and a 1950s Edgemaster paratroop automatic knife... for $25.
Also this week I got a Benchmaster 9100 automatic for $35, though it probably needs about $35 of repairs from BM customer service. Still, it's a $180 knife new.