fun with numbers...
$580 (retail of pro as stated Sep.1)
$550 (retail of 6800 currently)
"you will be charged only
the price difference of the handset."
580-550 = $30
"In addition to this, I can offer you additional $50.00 credit from my side on handset upgrade. So, you need to purchase the handset at the Sprint Store and after activating it just replay and we will apply the $150.00 ($100.00 previous promised +$50.00 promised now) credit on the
account."
$150 - $30 = $120
So by my math you should end up with bottom line of extra $120.
Of course they need to clarify, as they said this rather open-ended, and possibly entirely wrong.