Our insurance won't cover any type of formula until after 9 months, and then it had to be the "sole source of nutrition".(and breast milk only worked for one DS)
We signed EVERYONE we knew up for formula coupons. The 60yo secretary's husband got a hoot out of getting the formula samples in the mail. It was a joint effort by everyone in my office to keep our babies fed. I finally had to put one on Neocate

. We had to directly order that from the pharmacy, although it doesn't really require a prescription. It is made in Liverpool. We were getting some friends that lived overseas to bring us cases, but that only went so far. I finally checked eBay. Several people were getting it for their children for whatever reason didn't need it. I finally made a direct connection with one of them and she would forward the case to me as they were shipped to her home.
Her insurance was covering it 100% and passing on the formula for about 25% - about the cost of a regular name brand formula. That lasted until DS was 11 months and we were able to get him back on Nutramigen after they had an ingredient change.
So, keep checking around - it can be done. Our neighbor also with twins, quit working for 1 month to get WIC (just needed the formula) for the year.