Definitely not true (!) Over my last 30 years in retro mountain bikes - and even my other hobbies and interests like fishing, instruments etc. I can say with 120% certainty:
There are A LOT of people out there (with hobbies of ALL sorts) that spend a shit load of money on parts and their hobbies in general - although their financial situation is completely fucked up! They rather buy the next Cook Bros Racing crank set when it pops up instead of paying their rent or energy supplier. Let alone their insurances or any retirement provision.