If you cannot find a used bike as good as those, you just aren't looking hard enough. In a 5 minute search on Ebay, I came up with 4 completed auctions for good quality, reputable bikes with a full complement of quality components for less than $500. Here they are:
All of them are bike companies a long history of making good bikes. Also, when you look closely at the spec sheets, you will notice the bikesdirect bikes all spec off brand parts for the less-talked about components. The slap shimano or other brand name rear and front derailleurs, and sometimes brakes on, but all the other components that the average person don't know much about are off-brand - the cranks, bottom bracket, wheels, hubs, bars etc. These parts will often wear out faster and need replacing and/or frequent maintenance.
I don't work for a bike shop or anything, and would have to find an incredible deal to buy from a local bike shop. The fact is, the shops around me, like the majority of LBS's, massively overcharge for their new bikes. They are selling to upper-middle class customers who want to get into cycling or triathlons, and are easily convinced that they need this $4000 dollar bike for their recreational use. A bike that, I might add, will resell for maybe $2000 as soon as it is walked out of the shop. A lifetime free service guarantee might also persuade me to buy from a LBS, but most shops only offer one year of service, which isn't terribly useful.
I would also look at getting a book on bicycle maintenance. The necessary tools to perform most maintenance cost less than $50 total, and with a good guide book, this will keep you out of the LBS, where you will get charged $50-75 for one service you could easily do on your own. I would, however, recommend utilizing the LBS for more serious maintenance such as wheel building, and anything to do with hubs. Specific tools are expertise are needed for these jobs, and someone who doesn't know exactly what they are doing will likely screw up and require even more costly repairs.
So my recommendation to you would be to look around on Ebay and on various bike forums that have a classified section. You might have to wait a few weeks for a good deal to come up, but they are there. My personal experience isn't exactly in the price range on this thread, but I found a Colnago bike with an almost new drive train that would retail for $3000-$4000 for only $1250 used. It is still performing flawlessly.