They are both pronounced the same. These kinds of words are called "homophones", meaning they sound the same, but are spelled differently and have a different meaning. You don't need to worry, because context will tell you which word is being used.

"bye" as you know, means "goodbye" in a more casual, normal way. When you say "bye" you usually say it with a lot of lilt and tone. When you say "buy" you say it in a more boring way. Hope that helps!!

Thank you very much everyone for the help!

Thanks Alex.

I am a native English speaker and I pronounce them the same.