Well, what a glorious question. As one of the Dealer's this year, I'll do my best to answer those questions.
1. Cheaper than Lost World? Depending on the merchandise, absolutely. Lost World is a comic shop and their anime selection is varied and limited. Being a single shop they don't have to compete with other vendors in the same room so price is not as competitive there.
2. Selection of items. While I can't speak for other dealers, our store
http://AnimeFanZone.com will have a lot of items ranging from key chains, wall scrolls, tons of figures, pillows (full body style and really awesome), plush items, shoulder bags, pins, buttons and tons of Tomy figures ^^ We will also have Pocky and Ramune on hand! While the Union won't let us "sell" them, expect to see these items being packaged in with other deals.
3. Price. Depends on the items on hand and if other dealer's are selling the same things. Just remember when comparing prices you see online to what you see in the dealer's room, the "shipping and handling" charges are added into the prices. Online prices can be misleading when you see an item for $15, but after shipping it's $22. So just be fair when comparing prices.
I know another dealer will carry a bunch of DVDs and Manga and not too sure what everyone else is carrying, but I'm sure the selection will be varied. Come with a fat wallet and leave with bags of goodies!!!