Nonsense.
Home prices ABSOLUTELY reflect the balance of supply and demand. The cost to build a home has NOTHING to do with the price of a home. NOTHING. Many a builder has gone broke learning that lesson the hard way. Build a $90 million home in rural Alabama and then try to sell it. Poof. You're broke. Idiot builder. Likewise, a home in Beverly Hills that cost $35,000 to build in 1950 may very well be worth $6 million today, and again that has NOTHING to do with the original cost to construct said house. What matters is supply and demand.
Now, is "speculation" driving up demand? I don't see it. Perhaps some isolated regions (e.g. San Francisco and Denver) are seeing a little of that, but for the most part what I see are people buying homes for their own use, not buying 3rd homes in an effort to gamble that home prices will keep rising.
What you have to look at are the demographics. Are more people (i.e. demand) moving into a given region? Are more people being born in a given region? Is more land being made in that region? Are more homes being built there (i.e. supply)?
Other factors to consider that impact demand are interest rates. Are interest rates getting lower or higher?
Still other factors impact supply. Are building permits getting issued faster or slower in a given region?
But if you think that the price of homes should be related to the cost to build homes, you'll NEVER understand why the market moves the way that it does.