If your theory is that Ferrari's sales are declining due to not winning championships in the last few years, I must respectfully point out that the reality of facts absolutely destroy your theory.
Here are some stats for you (taken from Wikipedia):
2008 - 6587 cars sold
2009 - 6250 cars sold (note decline after a WCC year - totally opposite to your theory)
2010 - 6461 cars sold
2011 - 7001 cars sold
2012 - 7318 cars sold
I'm not an economist but the trend shows that I should bet on Ferrari selling a record number of cars in 201,3 despite the fact that they want to limit their production to make the brand even more desireable.
These stats also show how little influence the negative talk on F1 forums (that you cited) have on what is really happening out there.
My point wasn't that it would affect any sale in short term. As I understand the demand for Ferraris are bigger then the production and actually your estimate of growth would be wrong as I remember that they decided to reduce production to make cars more exclusive (not sure about this). Probably not many of us on theese forums are going to go and buy a Ferrari tomorrow, or McLaren based on last years WCC.
But the reason that Ferrari is in a league of its own is the story, the legend, the posters everything. Their most prized possession their name and its getting tarnished little by little. Maybe next time somebody watches Top Gear and they tell you about the smart aerodynamics you wonder how good it is when they cant get a windtunnel to work...
One in a million buys a Ferrari each year, many of those have dreamed of one day buying one since Schumacher era. As somebody said in one of the treads, Ferraris been here for 60+ years and want to be here when we are all gone. But for this to happend the myth must live on.