+1... What he said!Wrong.
By your definitions, none of the bikes you list are "collectible". Even the racebikes, which cost so much to produce, won't exceed their original value for quite some time. The SP, the R--none will ever outperform a normal investment. The nice part now is that bikes such as these can be ridden and enjoyed and will mostly maintain their value.
Not sure why you would consider the 998R more collectible than the bike of this thread. First, the frame and running gear is from the SPS, not a standard 996. The only difference with the 998R is the bore/stroke (for 3 more rpm, only at high rpm), a ventless CF tail, and slightly lighter wheels. However, there were 40% more manufactured and it will always be second. How does that work for baseball cards?
I wish I had been as eloquent in my response.