The Thumpertalk price
for an '06 YZ450F is $6199 with no more than $295 shipping plus the $9.95 membership (if you aren't one already). That comes to $6503.95 if I mashed the right buttons. At your local dealer you were looking to pay a total of $7300 + TT&L (how much is that, anyway?) if you count the value of your bike at $2000, or basically $5300 + TT&L for the bike. SO, again if I am poking the right buttons, you'd only have to sell your bike for $1203.95 to equal their deal (again not counting for the TT&L, so even less, really) if you bought one from TT..............AND you'd be supporting the site we all love so much. I'm sure you could sell your bike for more than that if it runs.
Now, having said all that, there is something to be said for having a good relationship with your local dealer. If I had the money to buy a new bike and was considering a purchase from my local dealer, one of the things I would try to get would be dealer cost + "x" percent for parts (which in general is going to be a far better deal than the 15-20% off that they will often offer). Over the long run, if you get that worked out correctly, the money and time saved by that "perk" you receive from buying the bike locally will probably outweigh the higher price that you are sure to pay.
Just some thoughts.........................
Good luck with whatever route you go.