I think anyone that bought quality knives long ago(and some more recent) would make a profit.
I've sold alot of my older knives, but still have several from the late 70's that I bought in HS while I was in our towns knife club. Most are worth about 400% more than I paid back then.
About ten years ago I bought a very rare older D'Holder at Blade for $500. I knew it was a great deal, but didn't know how rare it was(nor did the seller). I took it over to D'Holder's booth and was offered $1200 from a collector. I turned him down, and every year at Blade he would ask if I still had it, and up his offer. About 4 years ago he offered a little over $2000, and we made a deal. I didn't want to get rid of it, but I could tell he wanted it more than I. Thats the most I've made on a single knife.
I've also lost a little money on several I've sold soon after getting them. If I order one and don't like it as much as I though I would, I'll usually just list it for the same, or little less than I paid.