If you trawl auction sites for business liquidations, you can also usually pick up an actual rack for pennies on the dollar.

It doesn't even have to be a tech business; most random offices have a small rack in a closet somewhere with some networking equipment on it, and the whole thing usually sells as one lot to anyone with $50 and a screwdriver to remove the equipment from the site.

They're not hard to find as you say (you can even find them at scrap yards and such) - though then you can find the fun of getting the right mounting hardware to actually PUT things in the rack (and you get to learn the difference between telco racks (very common) and server racks (somewhat less common).