You're missing something that many/most states have laws that the seller/buyer must disclose, not the price the house is sold for, but how much of a loan was issued for the house. If they are not disclosing this then it's likely they are committing a crime by not doing so. The fact we are seeing larger amounts of 'paid in full' on houses is a significant anomaly and represents a change in market dynamics, and all changes in market behavior should be monitored. For example when we saw leading up to 2008 crash the "interest only loans", it was predicted by a sizeable number of people that a crash was happening 'soon', and in which it did.
Of course this varies by state, so other laws can apply.