Let's assume that the tweet is proposing to spend $10 billion per year to end homelessness in the entire US, since it contrasts it with genocide which is clearly a national objective not a local one.

A quick Google gives on the order of 1 million homeless people in the US. That's $10k per person per year which is the correct order of magnitude for the price of housing someone.

I believe OP missed the "per year" in the tweet that's why they are comparing to house prices rather than the yearly cost of housing, which is obviously much smaller because houses last longer than 1 year.