The difference between a $300 frame and a $3000 will be very significant.

You're looking at ~3-4 lbs of frame weight, and cheap Steel or Aluminum vs Carbon-Fiber and Titanium. The $3k frame will absorb bumps better, sprint better, handle better.

For reference, I had a friend try my Infinito ($3k bike) compared to his <$1k Motobecane. His comment was "I need to get one of these." We were doing an long up-hill section, so it wasn't shifting or anything just the raw difference in frame.