My two cents worth.....let's see....6 months worth of electricity, extra lights on, fan on, heater on, iron on, running either AC or heater, vacuum going, hot air dry gun in use, not to mention how many hours away from family and/or friends, and flying to dedicate to an airframe that doesn't perform any better than one it took 10 hours to get to the field?  Does that work into the equation at all? 
For all those that consider time not having a cost to it, I beg to differ.  If the comparison is factual these costs should be factored into the total dollar amount needed to kit build.
 
An ARFs linespan depends on how one treats their aircraft.  I see pilots throw incredibly expensive aircraft around the skies in a bipolar fashion that makes me sick.  Then they expect a build of any kind to withstand that constant treatment. They wonder why the firewalls detach or wings go separate ways and tail sections flutter lose.
 
I'm restoring an older Chipmunk and I know I have 2X the cost of an quality ARF into her already just in the restore alone.  Is it about the money, NO.  I use bad weather days, lousy TV nights to dedicate to her ressurection.  Is that time better spent on mentoring a new up and coming pilot on a SIM or being at the Club meetings or sitting with the family playing a board game with the kids, or taking the little lady out to a cozy restaurant to show her he's really the #1 in my life.  You can bet your life it IS.   

Kits are a challenge and also an incredible dedication of ones talent.  Cost wise, they cost 20X what an ARF does in time away from life (figuring 3 hours a night, say 3 nights a week, maybe 4 x 4 to 6 months = 192 to 288 hours).  Wait until all you young live forever whipper snappers get older.  I know one day you will reach that threshold of life to where you will find that interaction with those who love and respect and need you in THEIR lives is what is truly PRICELESS!  

ps...288 hours is 100 movies with the woman you told the Good Lord above you would "cherish and have and to hold" as you go to those movies men hate to go to, or 150 trips to the park with the grandkids, helping them down the slides and kissing the knee booboos so they quit hurting.  I didn't see those costs discounted in the ARF build.  Spare time doesn't have a cost (value)?  Hmmmm. 

OK I have my kevlar shorts on....take your best shot!  Aim careful please.  Don't hit this wonderful woman standing beside me tolerating my constant request to go flying when a brand new tear jerker movie just came out!