The cost isn't the cost of generating the patch file.  It's all the other things that have to change that make it expensive.  Most of those changes are not visible to the tz database; they are costs to the consumers of the tx database.  The database changes when necessary, not to be cosmetically more attractive.

--
Jonathan Leffler <jonathan.leffler@gmail.com>  #include <disclaimer.h>
Guardian of DBD::Informix - v2013.0118 - http://dbi.perl.org
"Blessed are we who can laugh at ourselves, for we shall never cease to be amused."