See also "Lego a 'better investment than shares and gold'" on HN 3 years ago[0] and the various Lego investment websites[1]. Not something I engage in myself, but have been aware of. Like the people who "invest" in trainers/sneakers[2].
[0] https://news.ycombinator.com/item?id=10791057
[1] e.g. https://www.brickpicker.com/ & http://brixinvest.net/