See my comment above.
You would pay 12% for 8 years not 30, because high interest rates drive housing prices down.
Also no, people wouldn't buy worse housing, it's a closed market. If no one can pay 450K because it'd be insane and you couldn't afford the monthly payments (you as a large swath of the population), the prices go down.
This is market economy with the twist that everyone needs housing, and the supply is quite fix.