Something to keep in mind as a general rule:
Big rods are cheap, small rods are expensive.
All things being equal, a vintage bamboo 3wt will be 2x the price of a 6wt. Light rods are in fashion today and much fewer were made.
A brand new decent graphite 6wt Orvis or Sage fly rod is $800. For $600 you can have a mint orvis battenkill 6wt impregnated bamboo rod from the 1960s. The cane goes up in value, the graphite will be worth $50 at a yard sale in 10 years.
I recommend fishing with cane, it has soul and is quite durable. It'll land many bass, tilapia and trout in its lifetime.