great! I can’t imagine having enough resources & free times (and of course SKILL) to do something like this in my lifetime

Yeah, ‘resources’ being the main issue here. Namely, money. I can’t even imagine how much money is in there, with so many LEGO parts.

Specially considering there is a lego millennium falcon that goes for something like 500€

Almost all of the mini-LEGOs there seem to have been custom made. At least the ones that I own and remember, are - AT-ATs, AT-STs, the X-Wings are the closest to the official mini-LEGOs.
He must have made them from spare LEGO parts, which doesn’t make this cheaper, considering it has thousands and thousands of parts.

Esse é um quarto muito fixe, tenha o rapaz paciência e dinheiro! Mas ficou muito fixe!

Pois ficou. Quem me dera a mim poder ter isto em casa. :P