Yeah, Queen is about 9, but even little more (especially in endgame), so:
If you became to put practical arguments, N+N+B≈Q, but B+B+N (if B-s are on different colors of cells) isn't, such as Bishops' pair is more than Knights' (but it's not 8 because board isn't fully free, and they can't be safe by standing near each other due to Queen's existence there).
Yeah, B=N, but B=N≈3.5 (average price).
So about Archbishop, it's possible to have its value slightly more than 7 as average value.
Yeah, Queen is about 9, but even little more (especially in endgame), so:
If you became to put practical arguments, N+N+B≈Q, but B+B+N (if B-s are on different colors of cells) isn't, such as Bishops' pair is more than Knights' (but it's not 8 because board isn't fully free, and they can't be safe by standing near each other due to Queen's existence there). Yeah, B=N, but B=N≈3.5 (average price).
So about Archbishop, it's possible to have its value slightly more than 7 as average value.