Tbh whats the actual problem with these 3 series. Would like to know if its in general the maint cost for the car or what.

Are you a BMW driver yourself? Maintenance already cost a fortune? Bring out your facts, don't just pluck figures from the sky.

Don't tell me you hear from this uncle that aunty blah blah blah.

I dont think bmw is the problem. I brutalize my e46 M3 & E90. No major prob except wear & tear. Heavy foot me. I drive nissan, volvo, kia, proton, honda, mazda, merc. But bmw 3series suit me well. Merc but luxury but not fun to drive except A series. Yes i will sell my e90. People will say so much 3series people sell bcos jump ship. But i sell to upgrade to new 3series. Right now got latest 2019 fortuner, camry 2.5, c250 amg, yaris in my garage. More relax on camry, more eye catching on c250, but this best still my e90. e90 parts & maintainance consider cheap.
Consider parts price to car value ratio. I got fen own workshop in pandan indah if u want cheap price.