Why don't they just ask for money from users? Have two versions: an ad supported one which people can easily remove the ads, and a paid version that doesn't come with the ad package by default, and maybe a few extra "premium" perks like wallpapers, themes, whatever that aren't in the FOSS repos together with extra backup space. They could charge on a par with OS X, say a total of $29 for the next two versions.
If you're referring to the price, well, that was covered by another comment.
Ubuntu's full of non-free software and binary blobs. This is why it pretty much works out of the box. There's little fucking around with drivers, non-free codecs, etc.
In any event, adding non-free "premium" features doesn't make the operating system itself any less free.
