I bought a bike that was a great deal (to me) basically about $900 off of a $2300 dollar bike. So at the time my budget was about $1K so that deal seemed to hard to resist and the bike fit me really well, so out came the cash and the bike into my trunk. So your deal very similar in terms of percentages begs the question are bikes marked up that much. I would have to think that at $4500 off (or my case $900 off) there's still some money being made here by the LBS and by the Mfr.
The question is should you go for it? Sure why not, if you have this kind of cash for a bike and it's what you love then why not.