They are on most auction sites but your best deals are going to be liquidation auctions. There will be auction houses that specialise in these in your part of the world.
You can look for second-hand components and machines at surplus industrial suppliers and auction houses. When an old product is deprecated, it's often cheaper for a big manufacturer to get rid of the equipment and buy new for the new product line, find out where obsolete equipment is going. It's not worth paying $100/hr for an integrator to repurpose with no warranty, but at hobbyist $100/week budgets that scrapyard is full of treasure. Some manufacturers and integrators will have "boneyards" of old equipment that they'll purge on occasion.
The article said that Teknik Clearpath servos are considered a great value, and they are, but even their smallest fractional HP 24V motors cost more than some name brand Allen Bradley (unofficial slogan "you can get better but you can't pay more!") 3-phase servos at my local supplier: https://www.surplusindustrialsupply.com/motors-mot.html
These places are like a garage sale for industrial lego.
