LEGO Modulars Massive Inflation?
At certain times of the year (particularly at the start of the new year) LEGO release new sets and at the same time remove older sets from their inventory. 

Also, in November and December in the run up to Christmas LEGO investors may take advantage of the increased demand by raising prices. Parents buying presents for their children would perhaps bid higher than usual as they are keen to get the right present and in time for Christmas.