Infant adoption opportunities are, to a certain degree difficult to locate. It is, therefore, the locating of the adoption opportunity that becomes expensive. If adopters want to let someone perform this function for them, they will need to be prepared to pay someone for that service. In many states, if adopters want to keep expenses down, they can take a proactive position and participate in the "finding" part themselves (through Internet profiles and other networking tools), and then use an independent adoption attorney or adoption agency to finalize the legal part of their adoption. This will often be the least expensive method of participation in an adoption.
A very common, real-life analogy would be the washing of your car. You have the option to pull it into your driveway, pull out the hoses and vacuum, and wash your car yourself. This will cost you the expense of the water and the soap, but may consume your whole afternoon.
If you don't want to bother with all that, you can always take your car to the self-service car wash and guide the magic wand over your car yourself, while still getting your shoes wet in the process. You may or may not choose to clean the interior yourself. This may cost you anywhere from three to five dollars in quarters and an hour or more of your time. If you really detest getting involved in the washing process, or if you are just busier with more productive things, you can take your car to a full service car wash (or even have it picked up from your office) where it can go through "the works", including a hand wash, a hand wax, a tire treatment, an interior cleaning, a new air freshener and maybe even a delicious mint. "The works" could cost you a hundred dollars or more.
Much the same is true in the world of adoption. You have a variety of choices available. If you want to put in the time and effort, a semi self-service option is available. If that does not fit either your personality or your lifestyle, a more full-service option is always available. The expenses involved in the different options will then be adjusted accordingly, depending on the amount of work that other individuals are asked to perform for you.
A note about international adoptions: Agency fees go towards the costs of arranging the adoption - from passports for the child to translation costs and legal fees in the child's country of birth. To ensure that you're working with an adoption agency dedicated to helping children, be sure to ask each agency how much money is routed into building new orphanages, or funding education or new foster families in that country.