I used to attend shows when I lived near some and had more free time. Now, I don't have the money or the time to waste on travelling several hours and hundreds of miles to shows. I especially don't have the money and time to waste on York--I can't afford the trip much less buy anything once I got there.
Were it not for eBay, I'd still be mostly limited to the Marx and MPC trains I got as a kid and the few pieces I picked up in grad school. The stock I have that hasn't come from eBay in the last 20 years or so has come primarily from the boards here, and I have been quite happy about those transactions. shows just are not a viable option for me.
Above, PhyllyReading mentioned that many eBay sellers don't post their items well, citing ignorance of the items' identity or scale/size. Some of my best buys have come from just that sort of auction.
Whenever I bid, I simply factor the shipping cost into the bid. If I can pay $100 for a piece, and the shipping is $25, I know not to bid more than $75. There is simply no way to get 'taken" on shipping when you know the amount beforehand. You may miss a nice piece, but another will come along.