So, when I first got hit with my nostalgia, eBay is where I looked. It was easy, convenient, and with a lot of reasonable buy it now prices, I was able to acquire the titles I wanted pretty quickly, and at reasonable prices.
I assumed that eveyrone that was collecting retro video games did this, but as I started to read more about the culture I found that eBay is sort of frowned upon by the "true collector".
I don't consider myself anything, except someone who loves video games old and new, and I get them any way I can. I'm not going to stop going to eBay for some games, but I am going to try to get them from flea markets and yard sales first.
Now that I've had a taste of a large flea market, I am definitely much happier with what I got for the money I spent.
At any rate, if you are eBaying exclusively to get your games, I definitely suggest finding a large flea market and keeping your eyes peeled for yard sales that may have video games the prices are MUCH better.