Flippers are good for the cue market because they add liquidity and in some cases are the "market maker" for certain brands. Although they buy at wholesale, they are taking a risk trying to flip a cue. They may get a lemon, may get burned in the sales process, have to pay high fees from Paypal and ebay. etc.
But say you have 100 guys flipping cues, each one has $5,000 in bought and unsold cues at any given time, that's an extra $500,000 in liquidity added to the cue market on any given day. Granted you're going to get 25% less from a flipper but you're also going to get the money.
You are correct though, they will intercept sales and then resale at a higher price to known collectors. I have more than once bid against flippers, lost and had them try to sell me the cue a short time later.
If a flipper is a seller on ebay, if he's smart you will never see him buying cues with that screen name. He will be buying them with another name than his selling account. Sadly, flippers are not always experts at the cues themselves, but only in the marketability. They may buy something that's been hacked up that all the collectors have already turned down.
Excellent post, sir, as well as the previous definitions. :thumbup: