According to Urban Dictionary: "an informal expression used to say goodbye" So, the pronunciation of "buh-bye" sound like "bub-eye". Hope this helps.

'buh bye' is the same as 'bye bye'. It is only used in speaking to someone with whom you are familiar.

The "buh" is a neutral vowel sound, like "u" in "up". It's also a weak sound. You could write the expression as "b'bye" and the pronunciation will be the same.

I think "buh-bye" is meant to be a phonetic transcription of how some people say "bye-bye".

Sorry, I didn't answer your question. It is pronounced 'bu-bye' ; the vowel 'u' is open, as usually pronounced in the south of England.