I have stock with both att and Verizon (pretty good paying dividends stocks by the way). So I follow the industry closely.
Verizon eliminated reporting "revenues per line" 3 or so years ago. Cause they were dipping below $50/line. (Example: $250/5 lines equals $50/line). Verizon and other carriers in the early 2000s/-2010 were mainly growing by adding non profitable 9.99 add a lines to "grow the subscribers". Obviously lines 2-5 drive down the revenues per line report. Especially with $400-450 a line subsidy with lines 2-5. Savvy customers would drive add a line (buy iPhone for $199 and get the subsidy and just put a flip phone on that line and avoid the data plan. Verizon wouldn't make any money.
Verizon than started mandating forced data plans on subsidized lines regardless if smartphone was used or not to combat that tactic.
Now the switch to shared data. And nickel and diming a $5 price increase PER LINE here and here. It all adds up.
$50/line is the key. Verizon knows that. Americans psychologically know that. What do we get for $50/line?
My current plan is $100 for 15GB data (+1GB bonus data ending sometime this year) and $15 per phone for a total $160 per month, or $40 per device per month. If I were to move to the "new" Verizon plan the closest plan I could move to would be the "XL" plan which would give me 16GB of data for $90 then $20 per phone which would be $170 per month. This moves my monthly cost per device to $42.50 so I would say you're 100% accurate when you state that the $50 per line is the target.
However, once my 1GB bonus data wears off, the extra $10 per month would bring me back to the 16GB data along with carryover data, safety mode, Mexico/Canada service... Why can't those extras be included in my current plan? Like you said, nickel and diming until they bring me closer to that $50 per line.
I hope people vote with their wallets and Verizon loses customers. T-Mobile is currently promoting 4 lines for $120 per month, that's really difficult to pass up as T-Mobile includes all of the "new" features Verizon implemented. (Note: it's 6GB data per line, so if you have a line that uses more than that, that could be an issue but for me this would work)