The CD, the CD-ROM, the VHS tape, DVD, mini-dv, dv-cam, PAL, NTSC, MPEG1, MPEG2, MPEG2 layer 3 (the famous MP3), Betacam, and countless connections such as for example firewire, DVI, HDMI, all the classical analog connections, and countless technologies are free for any manufacturer that builds them into its machines and only competition between brands for best performance is legitimate.
Think that a future HD-DVD with a movie encoded in MPEG4 will necessarily be more expensive only because the codec owners can charge the studio wanting to use it, for the minute.
The economic interests involved in compression codecs are unbelievably large and rather unknown.
Regarding technological differences between both codecs, it is a well-known fact that MPEG4 is more efficient than MPEG2 when using very low bit rates (which is why TV over ADSL will have no choice but use it ). However, if we use very high bit rates, which will be used by future formats, the difference is much less important.