My bad, I thought that was always a bit of a joke...
According to this formula MA7 is higher valued than AV9
viewtopic.php?f=4&t=38335
Which of course is somewhat arbitrary as all salary calculations are but it has some logic as MA is arguably better (applies more universally) than AV (which may not come into play at all).
If MA6 to MA7 is such a major leap is another point, but I guess it's somewhat acceptable (half-line to end-zone is 13 squares, so MA7 cuts it to two turns).
However, MA in relation to the board is a very weird thing in BB. I only once noticed that dropping from MA6 linemen to MA5 lineman felt dramatically slower.
Also traversing from one wide zone to the other matters (15 squares, or from wide-zone line to wide-zone line, 7 squares).
Anyway, I think there is a lot of depth in the science of MA in relation to the board. And valuing MA over AV is not wrong, but justified.
Edit: I guess one could discuss salary compared to a player's meta (pays for MA it doesn't use), but I think that would probably go beyond what a salary system is actually able of doing. Besides, how much would it actually matter if 40k got knocked off (10k per blitzer)? Neither Team (Human/Orc) is particullarly expensive to begin with.