While it makes sense to invest rather than paying cash for a car of the same value, that's probably not really what's going on here.

Most likely it's a guy who financed an expensive new car that he didn't have the cash for. The term is probably 5 or 6 years, and by rolling it into a mortgage he can cut his monthly down by a lot, even if the mortgage is at a higher rate of interest.

Cost of car | $ 30,000 |

Car loan rate | 1.9 % |

Car loan term | 5 years |

Car loan Payment | $ 524 / month |

Now lets throw this into the mortgage ...

Mortgage term | 30 years |

Mortgage rate | 4.0 % |

Car Payment Portion in Mortgage: | $ 143 / month |

Magic! His monthly just went down! How incredibly fucking terrible of an idea could this be? In 30 years, that shiny new car will be dust. Consider that if he is like most other hot blooded car sucking consumers, in 5 years he's going to want to trade up. Can he afford it? Let's find out:

Interest paid so far | 5,679 |

Principle paid so far | 2,880 |

Amount outstanding | 27,119 |

Cost of new car with trade in | 15,000 |

New Car Payment portion in Mortgage | $ 221 / month |

Woah! Who can't scrape up an extra $80 a month for a new model? Maybe while he's at it, he'll refinance his mortgage out to the full 30 years again. That would make the new payment $200 / Month. What a bargain! Take THAT, future self ... right in the nards.

Depreciating assets have no place in a mortgage. The reality is that folks will justify the entry price of a new car because they can afford the monthly when they do this.