Hmmm... but considering what you normally do on a netbook, I'd say paying to get a few features you actually will benefit and a lot of others that you won't, does not male financial sense.
There are already free programs that allow you to change the desktop wallpaper, on of those programs even allows the same effect of changing it once in a while; there is alos a free Aero enabler, and for your DVD needs, just download the free VLC media player. There you have it.
Windows Home Premium to Professional discounts though is a welcome addition, although it's just 10$. But hey, better than nothing, and comes with a XP license. I bet that is the main reason for the discount to be so little; and again, the reason for the Starter to Premium being so much bigger is probably because they realized they are not getting so many people upgrading as they thought, and probably becausue of all those free utilities that I talked about above.