I'd say BAND 3 is a very wide BAND; if we're talking about Tech, then in my LOB, the BAND 3 fella is the head of 380 people..I'm pretty sure he makes a cool million bucks as TC.
At the same time, I can imagine that the starting of BAND 3 TC might be around $500K.
The real problem?: very-very few people reach that level and the wait is not worth it in most cases, unless you're in a really-really critical tech team, which are only a handful in BofA and then your ascent is comparatively faster.
Yes band 4 is usually a Sr manager in tech managing 30+ or an architect. Band3 in tech is hard to get to and hard to see if worth the struggle. Was thinking entry B3 is 400k TC but I agree it's a wide band that goes to 1m+