I'm sorry...I forgot to mention that it is entirely possible, IMHO, to re-home without monitary consideration in exchange, and that adoption carries an implication of government or regulatory registration of transfer and often a previously registered entity...a child with a birth certificate already registered, for example.
Also, even in an adoption, there can be profit, which should not be excessive, or which may be siphoned off at some point by an involved party. Legal fees for adopting a child could seem excessive due the lawyer valuing his/her time at a higher rate than might be seen as reasonable...to a captive market, who must have a lawyer to file certain papers due to governmental regulation.
I think all of these factors...and I may have forgotten some still...play individual parts into the confusing subject of getting puppy from welping to our loving arms.