I think that I finally have it! A bike I really don't care about!
 

I have read time and time again about that bike.The one that people don't really mind if it gets stolen. I thought that I had one like that. I got my Trek 820 for sixty bucks. In my size. With a spare rear wheel and a trainer. It was a good deal. IT was TOO good of a deal! I knew that I could never replace the bike for what I got it for and then I started to put time and money into personalizing it and before too long... it had value! Not any real value mind you, but sentimental value. I have several other bikes as well. None of them terribly mostly, all things considered, but I had to work hard to get each of them and they all mean something to me. I would be quite upset if any of them vanished. Except one.

I bought my Fisher Advance for $75. It needed a back wheel. I had one laying around. Done deal. I wanted it to be just a MTB so I slapped on a set of WTBs that I had laying around. A QUICK adjustment of the shifting and... that was all. I have no appreciable time or money invested in it and while it is a serviceable bike, it wasn't the Greatest Deal In The World to buy and I can replace old 26ers all day long for what I paid for it or a little more. Of course, with those super-wide dirt tires on it and no racks or lights or any thing it's not really a practical ride for any thing other than trails, so that all I do with it. There is no "locking it up" any where. Pity, though as it IS the one bike that I wouldn't think twice about leaving locked up some where.

Trouble with nice but cheap bikes that you ride everyday is that you form an emotional bond with them. I don't think you can find a bike that is good to ride and that fails to bond.

This. And as the OP pointed out, even if you get a decent bike at a great price, you'll realize that you won't easily get that lucky again.