I would say most of my items have been bought used, primarily from Pentax Forum's Marketplace, which I truly appreciate because the sellers have always been so reliable (there was one notable exception -- someone who appeared once, sold one damaged lens and never returned). My first Marketplace purchase was an SMC M 50mm f1.7 that was described as "good condition" and was almost new in appearance and function.
Next up is probably KEH, as I've found their descriptions to be fairly conservative. So their Ugly seems pretty decent to me. Their Fair seems very nice, etc. I've never had an issue with KEH, but it is nice to know they stand behind their purchases, are fast, and reliable.
I've been known to find a few things on auctionBay, but often nearly by accident. If there's something interesting, I'll place a low-end bid. A little too often, even though my bid might be half or 60% of what past sales seem to be, I end up with the item. A little surprising, tbh. I've been watching for a particular lens and just "accidentally" picked it up for half the new price, box, pouch, and all.
Oh, I'll mention Robert's Camera as well. Although I haven't bought all that much from them, they seem "KEH-like" in their assessments of the gear I've purchased from them. Often, they'll have an item on eBay and accept offers $10 or $20 less than their reasonable posted price.
All my bodies have come used from Marketplace. Again, just the most reliable used source, imho. The oldest bodies (K100D, K200D) came from Refurbs from electronics clearance places (remembers all those great deals on everything back about 16 or more years ago?) As one popular online bargain hunter used to write, "Refurbs are often as good as new, because at least someone has made an attempt to assess whether they are fully functional."
Two bodies I found new were from back in the days when Pentax had clearance sales that were really bargains. The K-01 went on sale for super cheap. In pretty short fashion, so did the K-30, which was a wonderful body to use. Convenient and easy to keep around everywhere.
Edited to add: I did get a wonderful K-5iis body from Price Watch posts. Someone across the country posted that there was a K-5iis at a pawn shop in my metro area. (I still need to figure out how to search Craig's List all over the country -- dunno how they found it!?)
Anyway, I was at work and happened to see that. Jumped in my car for an early lunch, drove 20-some miles, checked it out in the store. They accepted $30 less than they had on it (battery charger wasn't correct, which I showed them), so I picked it up for half the price of a new camera with under 500 clicks on it. Wonderful camera, still.
The plastic 35mm f2.4 on it was caked in something that looked like baby food,
but cleaned up good enough. I never grew attached to that lens for some reason.
So, another extra big THANKS to the members of PF for their eagle-eyed sharing and kindness.
I found a 55-300mm PLM from Pentax refurbs and have been quite pleased with it. Hmmm.... what else? I'd like to buy more from Pentax directly, but their items are usually close to full price or they don't have what I want on sale or in their Refurbs at the moment. The way I look at it is that my used purchases help the sellers keep buying new stuff, so I'm boosting Pentax that way.
I only buy used cars, from 2-4 years old. Saved me thousands over the years. A new car is worth 20-30% less the moment it hits the public street. Took awhile, but I learned that lesson while still young, so no new cars in forever. A similar approach to photography makes it much more affordable to try out "the good stuff" and not end up broke.