There's a risk that this oddly named (oh wait, it's Glide Stream, that's almost normal heh) series will cost more primarily for their looks, but we'll see some day.
The expected cost in the article I linked to seem to be "reasonable" for such quiet fans, my hope is that the "Slip Stream" fans will drop in price and will continue to be manufactured, this would help everyone who wants so silence computers as this will automatically generate a price war which is always beneficial for "us" the consumers.
That rubber for instance, would be unnecessary on Slip Stream 120's since they simply don't vibrate. At the very least not the speed models "we" go for.
I have no problem with Scythe adding these rubber pads, not least because it wont hurt to add them (especially on heatsinks, which are far more prone to have 50-60 very thin aluminium fins vibrate) as well as those models that are higher rpm or are PWM fans that can spin up to higher levels where vibration is more likely and reducing it is a good thing. Adding to this, some newer Antec fans (as well as others) now have rubber dampening on them, again this is something that is very good for the consumer as this is likely to catch on with other manufacturers, which is a big boon all round.