...it's not nearly as cheap to by locally as it is on GB, and in some cases, it's a lot cheaper, as in hundreds of dollars saved...
I'm very surprised to hear this. GB being an auction, and auctions are designed to bring the highest price possible. Typically, the more bidders at an auction, the higher the bidding. (This is stuff we all know-nothing new here.) But, with GB essentially being a nationwide auction, with a
lot of bidders, I'm surprised to hear that anything sells cheap.
I also don't do any business at ebay, and for the same reasons that I don't do business at GB. Anytime I try to sell something, people want to pay pennies on the dollar, but when I try to buy something, it always goes for 80-90% of new prices. (I see the same phenomenon at yard sales, pawn shops, Facebook Marketplace, etc.-anything in the secondary market really.) Add into that the high probability of being ripped off, and online auctions just aren't of any value for me. (And, due to the prevalence and ease of online auctions, live auctions are a thing of the past.)
Just about the only value I see in GB, ebay, etc., is the ability to easily find long out of production, collector status items. Even with that, you have to take into account all of the problems and risks previously stated.