It's good to read I'm not the only one who strikes out at garage sales, etc. Years ago I used to go to those neighborhood garage sales but don't waste my time anymore. I encountered too many people as described above that think they're going to get rich selling some model kits or forgot what "garage sales" were originally intended to be.
Flea markets or swap meets are just as bad. I never understood how the seller could possible know the actual price he wants on every single kit he has when the price isn't on it. You've really memorized all 100 or so kits prices in your head?! Maybe you should be doing something more productive with that kind of brain power.
We had a neighborhood garage sale some years ago and I had about 30 kits all priced at $5. Never sold any of them.