u/JGA_PeanutButter145

I was told by a one time singing teacher that my attempts at harmonising turns into pure key transposition instead of diatonic movement within a song's key. He suspects I have some sort of perfect pitch as apparently a downside of it is making It difficult to stray away from the melody if my ear is untrained.

I've tried testing myself multiple times, playing a note and guessing/singing the third,, but I seem to have it stuck in my head that the interval of every third is the same as C to D which makes me think every note's third is just 4 semitones which is obviously not the case.

How do I train my brain/ear into figuring out harmony relative to the key instead of purely transposing chromatically?

I saw people comparing steam decks and Nintendo switch 2s and they mentioned how close they are in price, therefore a steam deck is better because of the flexibility. If I am not mistaken, NS2s are around 28k at the moment, and steam decks are 40k - 50k. Have I just been seeing inflated prices?