That's true regarding the big international events - they've discovered that even the poorest JWs are willing to pony up thousands or even tens of thousands of dollars to get treated like "rock stars" for 7-14 days.
I know several who have drained virtually their entire life savings to go to one of these things. Then when they get back home, and the buzz wears off after 3-4 days, they immediately start trying to figure out how they can do it again.
I suspect that in the future, nearly all regional conventions will be very low-key, likely held in assembly halls wherever possible, and the glitzy no-holds-barred international conventions will be held every year up to their saturation point (when they run out of JWs willing to pay tens of thousands of dollars to be treated like a rock star for 7-14 days).