Even if Netflix was like "Go ahead, share your account with everyone you know" (which they aren't)... expecting Blizzard to operate in the same way as Netflix is silly.
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Yes, but what you paid for your subscription last month is the same as what you pay for your subscription this month...you aren't paying any more to get classic than you would just to play BfA. It might not be, strictly speaking, "free"...but there is no extra cost.