Bubbles burst for a lot of reasons, some of them having nothing to do with the quantifiable fundamentals. One day a bunch of people wake up and decide that the $600,000 two bedroom condo may be worth $550,000 in six months or banks decide not to over extend themselves. Bubbles have to do with individual and institutional perception of value.
Can you identify the last real estate bubble that burst without any quantifiable fundamentals? Your suggestion may work in a local or small regional situation but cannot be applied to a broader market. Perceptions, rational or not are driven my something that can be identified.