To add to Cajunscott's reply, it's probably easier to be cheaper when the cost of the dinner and entertainment are shared amongst 50 people than amongst 20 people. I'm not sure how many people attended Tokyo's Burns Dinner last year, but I have to guess that it's not as many as one would think. Add to that the value of the yen/dollar over the past year and it just seems more expensive this year.

Sorry to hear you can't go, but I'm with the others. Host your own little Burns dinner.