Value and price is different concept

Goverment is smart too. It is very easy for IRS to figure out all history house value. e.g: they will call county assessor office to order a property history value information. Goverment also have a AVS index for that. There is no need to be accurate. They just need to know the rough figure, most time is at favorable homeowner figure. If homeowner is unhappy that, you can appear to the court.