No offense taken, and the battle of used-store vs. streetcorner/ebay/craigslist vs. new is a difficult and complicated situation. In the end, all anyone wants to do is "get on by" without upsetting people, but all these things seem to be in contention with one another for one thing: your dollar.
I could say how we don't normally set our prices at "just below retail": most of our prices are determined by what we research online (for media this is usually a quick check on Amazon) and we price them as such, unless we're POSITIVE it will sell for more. We've also ran into some competition with Walmart, actually, where they price their brand new blu-rays and some consumer electronics items at or below USED value (which tends to be ~60% retail on average).
As for what we pay, it reflects the risk we're taking on what we buy. A vendor has the ability to get replacements or refunds if there is a significant amount of a defective product; for us, it just goes in the trash. We have to do our research, hold it for a number of weeks to be processed by the police, clean it, maintain it, and then guarantee it - all after buying this thing from someone that decided to use their DVD cases as coasters. Fantastic. $10-$15 for something we're going to turn around and sell for $30 sounds more than fair to me, but I suppose I'm biased.
The issue isn't that people are buying and selling between each other instead of us. It's using our facilities, our store, as a way to find that connection. Go use craigslist or ebay - we refer people there all the time when they don't like what we're willing to pay - but it's akin to us coming and selling our crap in the middle of your store and saying that it's OBVIOUS and INEVITABLE because you're selling everything SO FAR ABOVE market value.