Being able to build a tiny ADU behind one’s house in my MCOL city isn’t very appealing because it might cost $300k+ AND increase the property taxes substantiall

Being able to build a tiny ADU behind one’s house in my MCOL city isn’t very appealing because it might cost $300k+ AND increase the property taxes substantially. My impression is that many people considered it and then scoffed when they realized that the ADU would cost almost as much as they originally paid for the (much larger) main house and lot a decade or so ago—and at a much higher interest rate if borrowing is involved now.