You can unsubscribe to Special Offers on a K4 SO. It will cost you $30 though.
To unsubscribe, go to your Amazon Manage Your Kindle
/ Manage Your Devices
web page. In the Subscribe
column, click Edit
next to your K4 SO. Follow the instructions on the screen that displays. You will be charged $30, which is the amount you received as a discount for buying a K4 SO model.
Apparently this option is not available for K3 SO models, at least not on my Manage Your Devices web page.
So why is this important? Well, a lot of people requested this feature for their K3 SO models. I think some bought them not understanding what they were buying, while others changed their minds after receiving them. This means that Amazon listened and built in the unsubscribe feature to the K4 SO. Those who mistakenly purchase one or simply decide later they wished they hadn't, can now unsubscribe. It also means you can purchase a K4 for $30 less to try it out, then if you cannot stand the Special Offers you can unsubscribe and pay the $30 you were originally discounted. Also you can even keep the K4 subscribed long enough to save $30 in offers and that will cover your out of pocket for the $30 unsubscribe fee. That is, since you saved $30 or more in offers you really are not out of $30 when you unsubscribe! That is what I plan to do.
BTW, I saved enough on my K3 Special Offers from items I would have purchased anyway to buy my K4!
Thanks to @Blossom for pointing this out