iPod Touch Upgrade charge with iPhone?

[McAlsop]

I have an iPhone 3g and two iPod Touch that are using the same Apple Store Account. Will I have to pay the $10 upgrade to 3.0 for each Touch? Or will it just be one purchase? Or even zero since I get a free iPhone upgrade?

I didn't have a Touch last year during the 2.0 upgrade, but hopefully someone knows. Thanks!