Yes, it will be something alright. Prices for accommodations will be higher if you can get accommodations at this point.
I hope they don't do what happened in Kyiv for the Eurovision contest. I was going to go, but then I discovered the hotel that wanted about $100 a night last year wanted over $1,000 a night for Eurovision.
You wouldn't catch me in Budapest those two weeks. I sort of suspect that if the number is 100,000 total, then at any given time the number will be less as this thing drags on for two weeks; but still nutty. I have a couple of friends who have picked up some part time work as result. Its going to be good for the economy. There might be some benefit in being there before hand as the town will probably be spruced up a bit. Afterwards??? Might be a bit messy. Who knows. Good catch Joseph.