Mobile,

There is nothing legal or illegal about this. You are not breaking any laws.

Now, look at it this way. If you cancel your agreement with Nextel after getting the phone for $30 you will have an ETF (early termination fee) of some $150 - $200 (check the contract for the actual amount if you intend to do this).

Add the $30 plus the ETF (plus the activation fee plus any service used to get an actual cost) and see if it is lower than the price of the "boost" version. If it is lower, then buy it from Nextel, cancel the service and pay the bill they send you.

My opinion is that this is most likely not worth the trouble. Without looking I am willing to bet the Boost price is less than all the other stuff added up. You also need to figure your time to activate then cancel everything.

There is an reason the Nextel phone is cheaper, it is because you are agreeing to stay on service. The actual cost if the handset is significantly higher.