I would not be so quick to write off the US East Coast. After all, the 2004 Worldcon was in Boston, and there continue to be discussions of a DC-area Worldcon bid (hamstrung by lack of facilities for now). And I have not heard of facility costs being markedly different in the east than in the rest of the country.
What I do think is that the old zone system allowed people to be a little bit lazy. Two-thirds of North America were disqualified every year, which made it easier for the one-third that was eligible. Now, with most sites eligible every year, you have to work harder on your bid because you're more likely to see competition from somewhere, not less as many people were predicting when we adopted "no-zone."
no subject
What I do think is that the old zone system allowed people to be a little bit lazy. Two-thirds of North America were disqualified every year, which made it easier for the one-third that was eligible. Now, with most sites eligible every year, you have to work harder on your bid because you're more likely to see competition from somewhere, not less as many people were predicting when we adopted "no-zone."