Don't know what the 2013 vs 2014 dynamic is now so can't help there. I went with the $275/mo all in deal myself and am loving the car (and the HOV sticker!). Ask for Matt Mariani at Duarte Nissan. Great guy and he should give you a good deal. No hassle and very straight forward. Hands down...
Did you ever end up finding pricing better than the $255 + tax? I was just able to get the following in LA which is essentially the same deal I think. Appreciate any updates you or anyone else has.
2013 Model S + Quick Charger
36 month / 12,000 miles
$0 down, $0 drive off
$275 a month...