I've done quite a bit of homework about adoption both from private agencies and through the state. Even with the costs of running an adoption agency factored in the cost is still prohibitive for many, otherwise perfectly suited adoptive parents.
We decided to adopt through the state and use the money we are saving to provide a private school education for the children we adopt along with other financial considerations. Basically it came down to using the money for the child after it is in the home rather than before.
ANY cost to adopt a child is worth it but in the real world we found saving tens of thousands of dollars to use for the child was more practical than using it to get a child.
Sounds like a great choice - Gods blessings to you and your whole crew! (Don't tie the leashes to the stroller!)