You must pay an adoption fee for each wild horse or burro you adopt. Usually BLM will charge you a $125 base fee. BLM will not charge you an adoption fee for orphan foals.
Yes, BLM may increase the adoption fee. BLM may hold competitive adoption events for wild horses or burros. At competitive adoptions, qualified adopters set adoption fees through competitive bidding. For these adoptions, the fee is the highest bid received over the base fee of $125. Horses or burros remaining at the end of a competitive adoption event will be available for adoption at the established adoption fee.
43 C.F.R. §4750.4-2