Why are these pistons so cheap on this site?

They're speed pro. They're the same cheapies you can get at Advance Auto, Auto Zone, etc. They're good, just nothing fancy, and that's more than they cost in a set. Yes they come with pins, no, they don't come with rings..

Edit: The set I bought also came with the wire locks for floating pins, but if you're buying 360 pistons, they probably won't, since they never came stock floating-pin.