I do this a lot now.
Estate sales, resale shops (Goodwill, Habitat for Humanity ReStores, etc.) are great resources. As more and more millennials are dealing with their parents' estates, they just don't want to be bothered with unloading stuff that they deem to have no value to them- so they just donate it or hire somebody to come and take it away (who usually just ends up donating it for the tax writeoff anyways).
You usually have to dig through a lot of crap tools, but I have walked out of these shops with some great "pennies on the dollar" deals on high-end stuff, and it all goes to a good cause.