Tax kills every deal. Remember that the only two inevitabilities in life are death and taxes.
I just verified my receipt for my last Loblaws protein purchase, and indeed I was charged tax. And I was charged tax on my www.CanadianProtein.com samples purchase too. Going by that, I'm assuming from here on forth that I will be charged tax for protein, which really is a non-grocery sort of item that would otherwise be tax-exempt. On a related note, I was slightly surprised to discover that cashews (which I love to put in my protein shakes) aren't considered groceries at Loblaws either, so I was charged tax on them too.
EDIT - The price calculations I have performed in this thread do not factor in tax unless I have indicated so (such as with the www.CanadianProtein.com samples). It's a base price (before-tax) calculation. Otherwise I'll be sitting here all day calculating prices for all provinces with different tax rates. Assuming I will always be charged tax on all protein purchases, I figure I can ignore including taxes in my math, which makes comparing the different results much easier.