People buy bitcoin because they think they'll be worth millions some day, but who should be the fool buying for 1000$+?
Has this question been answered before?
Mark Zuckerberg? LOL

maybe layman with more money will buying

Maybe he is the real Mark Zuckerberg

, but I'm not sure. However I think the people will buy also bitcoin if it will raise to 1'000 dollars.
dude, when btc is 1000$ people will buy doge or litecoin then or some other (in relation) undervalued coin. Altcoins will be booming later, no doubt. But all that is aswell just speculation demand.
We already found out: merchant adoption does not help raise the price because merchants do not hold it. So there aren't that many usecases left which could create REAL demand.
Anyways, keep the answers coming. Who is buying that expensive coin later?