Well, you can pay quite a bit of money for a quality aviary from a specialist builder (Trewin Aviaries, Clive's Quality Aviaries and D&S Aviaries are great). Or you can buy a cheap aviary kit from Bunnings. Or Gumtree often has some good, cheap second-hand aviaries.
Thanks,
Aidan
Aidan [] Junior Moderator [] Breeder of Native and Foreign Finches
Queensland Finch Society Member
2019 ABK Magazine Young Birdkeeper Winner