There is a marked seasonal cycle in many housing markets. Sale volumes and house prices are significantly higher in the Summer and lower in the Winter. Evidently there should be some arbitrage, by selling high and buying low and renting in between for those who are genuinely moving or simply holding on to real estate for speculators. Possibly, the transaction costs are too high for this to happen. Or maybe the market for houses is not fluid enough for price not to cycle in a predictable way.
Cemil Selcuk picks up on this second idea and builds a search model where the supply is smaller in the Winter in the sense that the probability of finding an appropriate house is lower. As a result, there are fewer successful matches in the Winter, and they happen with a lower price because of the discount cost of waiting for better opportunities in the Summer and because the matches in the Winter are of lower quality. This is a rather trivial theoretical result, and it would be nice to know whether it approaches quantitatively the seasonal differences that are observed.