Where to buy the best 'LABNEH' (fage) at the best price?
The Fage brand doesn't seem to be available here, despite the large Greek population in the GTA. However, the product you want is probably more widely available than anywhere in the US.
"Labneh" is simply strained yogurt in various mid-eastern languages. The Greek stores may just call it yogurt, possibly appending terms such as "traditional", "pressed", or "shepherd style".
You will find in at virtually all mid-eastern and Greek oriented stores, and many Jewish and Russian stores, including supermarkets in relevant neighbourhoods. It will be in the dairy case AND in the deli/cheese sections where a store has both. At mid-eastern stores (such as Nasr and Arz), there will be flavoured and marinated versions in addition to plain, some still creamy and some in the form of semi-soft cheese.
I can't name a price off the top of my head, but it isn't terribly expensive. It's also very easy to make your own. Get any natural plain yogurt at the butterfat level you want. I prefer Liberte 10%, but you can use lowfat or nonfat if you insist, Western, Astro, and M-C make similar products, and there are more brands available in the ethnic stores. Just do as chloe103 suggested - put it in a cheesecloth lined strainer over a bowl and let it sit and drip. Stop when it reaches the consistency you want. You can use it flavoured or plain, sweet or savoury.
Fage is a brand name, not a foodstuff. Fage is a Greek company that makes and imports yogurt. Their yogurt is, as is traditional in Greece, strained of whey, and thus much thicker than most yogurt we see on this side of the ocean. It is totally fantastic; sadly, I believe that it isn't available in Ontario.
Labneh is the generic Arabic term for strained yogurt. There would no doubt be some subtle differences between any brand of labneh that you find, and the specific yogurt made by Fage, but you can think of them as close cousins.
Because strained yogurt is much denser than yogurt that has all the whey left in it, it is more expensive (i.e. a tub of strained yogurt will cost more than the same-sized tub of unstrained). I definitely think it's worth it, but I'm not sure how you'd feel.
You can also approximate these goodies at home by straining yogurt yourself: set a fine mesh sieve or a double layer of cheesecloth (held up with a rubber band) over a large bowl, and pour into it a tub of your favourite plain unsweetened yogurt. Leave for a couple of hours. In the bowl you'll find the watery whey, and in the sieve a much thicker yogurt. Again, because it's much denser, you'll find that you've lost a lot of volume - I typically end up with about 1/3 less.
Any my favourite thing to do with it is spoon it over fresh fruit, drizzle with honey, and scarf by the bowlful.