Unless there is saturation of a product, Ebay definitely helps It's an important medium. I remember pre-internet & Beckett, buying some fantastic 50's & 60's collections back in the early 80's for great prices. Prices were left to the seller & buyer to hash out.
Everything permanently changed right around 1985 & about the time Beckett & Sports Collectors Digest took off. It became a national hobby instead of being regionalized.
As a kid, I remember scanning the Sporting News for the card ads in the back from Larry Fristch & others. The only other place to get cards was of course the local grocery store & some toy shops.