This is all accurate for "new" subscribers starting today. I agree that if I were to sign up for ATT right now, I'd opt for Next on the 10GB shared plan, where an additional line costs an additional $15.
However, those on contract before 2/2, the options become less simple. Anyone on contract before 2/2, may opt for the 10GB shared with $15 per line. The longer a contract remaining, the more compelling value this becomes. For lesser data plans, the price per line is $40, unless one were on contract 6 months prior to 2/2, in which case it becomes $25. Which is the better course for these people depends on data use, time remaining on contract, and each respective case needs to be calculated on an individual basis.
Then, there are those (of which there are many), like me, who have the old grandfathered plans, 450 shared (with 7k rollover minutes awarded), 3GB data, and free 6 month texting for approximately $100 for 2 lines, once all discounts have applied with fully subsidized new iPhones at the $199 entry price. Throw in the orphan 3rd dumb-phone line for $9.99 for an early $199 iPhone upgrade, the case to switch to the new plans becomes much less compelling.
What you call exploitation, I prefer to refer to as maximizing value. Just as ATT has tried to maximize shareholder value (by exploiting consumers), I've chosen to maximize my own value in return, by exploiting them.