I've had a Knapp 410 and found it was a great machine. Bought it used on Ebay, drove to Las Vegas to pick it up. At that time (2008) I was able to get several replacement parts from Laguna (it took a trip their office in Irvine). I doubt they still would support them, so you would want to be sure it had the accessories you needed and it was in good shape. Unfortunately l sold it when we moved and my shop downsized. Finding them used (or 16" J/P) is very hit and miss. I bought a MM CU300 used last year. It was a very good machine, but I missed the 16" J/P, so I just sold it. It sold in 1 week on CL, whereas it took 3 months to sell my Knapp. Now I'm back looking for a 16" Combo for J/P & Slider.

Location plays a big part in finding them used and in pricing. As you mentioned above, there is a Felder BF-741 for $20k in San Jose on CL. The same basic saw was just on E-bay for $6900. It did not sell, as it is located in Mississippi and the seller won't ship. (I checked). Patrick I'm not sure where you are located, it might be an option if you're not too far away and open to a drive.

One other factor to consider if you are buying used is having to get it home. Having move 3 combo machines by trailer, I can tell you they are a challenge. The 16" machines weight 2200-2500 lbs. I rented forklifts to load them. Yes they had mobility kits, which work fine on level concrete. Pulling them off a trailer or over dips/bumps is something else. You need at least a pallet jack. Separate J/P and sliders weigh less, usually 900-1100 lbs. Still heavy but easier to get home and move in the shop.