Ok you can all see that im new to this stuff but i picked up a fixie not to long ago and its just an sold concord. and my question is what make this a $50 frame and other 80's or 70's frames worth so much more. i see some are hand made and what not..what els make stuff like bridgestone bikes frames worth 500+ .

Side note i think im going to start riding my bike to garage sales looking for rare old bikes. so i want to know what to look out for. im getting an idea for some of the brands to look out for. but even then i see Bianchi frames for $100 to 500+ for what looks to be the same frame. any help or a link to a post with the info im looking for.