No, they're not all the same - different blades are made from different alloys, are sharpened differently, etc. High priced metals and precision sharpening costs money.
We cut 7 days a week in our online shop. We use only 60mm Martelli blades, because they last a long time, usually 6-8 months each.
I tried HF blades once -- the first one wasn't sharp enough out of the package, the second one lasted about a day and a half and wasn't that good during that time. The rest got pitched in the trash.
HF blades retail for about 50 cents each -- Martelli blades retail for about 5 dollars each, so Martelli blades cost 10 times as much.
However, I can get 180 to 200 times as much life out of them, not to mention not spending my time changing blades. And, they cut better from the get-go.
Which is the better bargain? It's simple math.