How rare is 6 sp manual trans?

[notaminivan]

My buddy is selling his 2006 E53 that has the 6 speed manual transmission. How rare are these? He seems to think that he will receive a premium because they are hard to find. I am not so sure. There usually is a reason why something is rare, like limited demand. On the other hand, since you cannot get an E70 with a manual tranny, who knows whether there is pent up demand for a 2006 with a 6sp.