If you do not have insurance you are required to purchase the full at retail price or find one somewhere else. My mother doesnt have insurance because you pay $7 a month and then a $50 deductible. If your phone doesnt break in a year you will pay actually paying $134 for a new phone. She finds her phones for about $10 on ebay and she likes them.
However if you are someone who has a droid, droid eris, blackberry or an advanced phone not having insurance would have you paying around $400-$700 for a phone. With insurance you just pay $50.