Premium domains can be mainly found in Bargain and Auction sections of this site. Just look at the thread titles to quickly find as many as you need.
Mostly they sell at $20 and below.
Those include but not limited to "Chinese premium" domains like 7N.com (selling for around $10 apiece), 5L.com (below regfee), 4L.biz (~$10) and so on... Sometimes most rare and valuable ones like 5N.ws or 3L.io can be also referred to as "gems", don't bid on them unless you can really afford it without falling into debt.
Recent Goldman Sachs domain market research shows that on the average adding "premium" to a thread title increases winning bid amount by approx. 20% (or $2 in absolute terms)
Keep in mind though that asking sellers why they sell their "premium" domains for less than a price of a pizza is considered unethical and offensive and may result in a temporary ban from the forum.