You are not looking at it right. Each line on the phone has a contract, so you would have to look at the line of the person that wants to leave, and see if they are month to month or still under contract. If that line is still under contract, the ETF (Early Termination Fee) is $175 - $5 per month you have gone through the contract for a basic phone, and $350 - $10 per month you have gone through the contract. (Ex., a basic phone that you have had for 16 months, the ETF would be $175-$80 (16x$5) = $95.)
As always, you should ask Verizon what the ETF is, they will give you actual $ amount.
If you are paying $160 / month, you must not have any smartphones with 5 people on it.