Sellers can put whatever price on a snake they want, but bear in mind that buyers ultimately set prices. If no one wants to pay four times what you did for that snake then the seller ends up taking the snake home.
I can see sellers at expos setting prices a bit higher to allow some wiggle room for haggling, and to account for the fact that the buyer has the chance to inspect the snake in person for any health issues, and because the buyer doesn't have to pay for shipping.