You mean buying domains cheaper than the actual cost of a dot com?
Is it possible to buy a "used" (lol) domain for less than a "new" fresh domain?
Yes. It is possible. You actually have several options here, but you have to be careful with each of them.
You can get an existing domain (kinda useless), an existing and established domain, or a dropped domain with an existing PR/history and plenty of backlinks.
For existing domains and established domains I'd go to the Sitepoint Marketplace or Sedo.
For dropped domains, just do a Google search for "dropped domains." This will provide you with slew of sites that actually go through the trouble of compiling the lists of dropped domains for you --sometimes before they're actually dropped.
You can buy an existing domain (with content) fairly cheap (25-100USD). You may get lucky on occasion and find a domain for 10-20 dollars, but it's extremely rare unless you're going the dropped (or soon to be dropped) domain route.
Now for the warnings:
When buying an existing/established domain, you want to make sure it isn't a dropped domain --unless you happen to be OK with that. A lot of domain resellers will not tell you they're selling you a dropped domain. Run a whois query at domaintools.com and go to archive.org to verify the history if you can, or you may lose inbound links. You might also wish to verify the domain is completely legit and hasn't been banned for anything (i.e. spamming).
If you are interested in a dropped domain, again, do your research. Find out why the owner might have let it lapse or dropped it.
When all else fails, I believe DomainMagnate is an SME on this topic.
♥ ( ★ ♣ ♦ ☋
♥ ( ★ ♣ ♦ ☋