Disposable items, things with a lifespan of less than 5 years, do get thrown away. These days, most of the custodial and maintenance staff will have gone through it first.... What quality you saw is a rarity around these parts...
In Texas, by law, new items of Capital Outlay that has a lifespan of 5 years or more have to go out for public pricing or public bids. By the same token, furniture, computers, and maintenance or educational equipment that passed its worth because of high repair cost or damage have to be sold by public bid or auction. There is a nation wide public auction website where you can get automatic daily updates of your state and any neighboring states for schools, universities, and even cities to put things up for sale.
Public Surplus: Government Surplus Auctions
Chances of finding a lab table, shop workbench, or other high dollar items beside a dumpster are almost zero around here.
I had to laugh out loud as I wrote the first paragraph. I remembered what one maintenance worker told me about what some of his friends did while setting up for one of the public auctions. By asking the I.T. department's members as they brought them in, some of the computers still worked, but most didn't. When the computers were put out on folding tables, the maintenance workers took masking tape and on the ones that still worked, they wrote words like "Burned out", "Shorted Monitor", and "Doesn't Work". On the Saturday morning of the pubic auction, the same workers were front and center to bid for those marked computers and got them for almost nothing....