Third, and maybe most important, neither player is exactly sure about the size of the pot: I don't walk in knowing that the dealer bought the table for $50, and I may not really be sure I value the table at $400.

More importantly, the dealer is even less certain about your value of the table, and both of your impressions of the value of the table can be updated due to the evidence of the bids the other party makes (assuming there are social components to the value / other buyers exist somewhere). As well, the seller's fixation on $50 is a sunk cost, as mentioned by STL and Kaj_Sotala.