Running network cables is supposed to be done by a licenced cabler, and if people want to be sure everything properly certified, then you will have to pay the dollars for it.
Of course, if you do have some knowledge in cabling and have the confidence to do so, even though you may not be licenced there should be no huge issue in doing it yourself.
At the very least most people can run some cat6 (or similar) cable throughout their home whilst being built, subject to their builder allowing them to do so... don't run this cable right alongside with your 230v cabling though! Once cabled, you can then get your licenced cabler in to terminate the cables pre-laid.