That 900 k that they mentioned takes into consideration inflation. If u convert 900k to today's dollar its less than that.

$3500 in future convert to today may only be $1500 (my guess coz I dun know the inflation rate they used). For $1500, its enough for basic living ie food and transport. No holidays, no cars, no shopping and assumption that all ur debts r clear.

If u buay tahan with $1500 a month, then too bad u dun retire, just keep working or pray ur children will support u. This is a simple fact doesnt need a rocket scientist to work that out...