That's not a sound argument though. It applies no matter how much you spend. The "real cost" of solving homelessness could be much less, and that could just be a particularly expensive and ineffective solution. Structural, endemic problems likely require structural, foundational solutions.
Either we're spending enough money that people can afford to live indoors or not.
$375/month is obviously not enough money for anyone to afford to rent anything anywhere.
Accordingly, the real cost of solving homelessness is more.