Let's imagine that I want to buld a wall 5 bricks long and 12 courses high.

http://www.ibstock.com/highlights-brick-calculator.asp

You see, on the brick calculator, that if I did that the area is exactly
1 square metre. You also see that it would take 60 bricks. That tallies
with the brick quantities on page 13 of Ibstock's Guide to Good Practice
cataligue.

What I understand is, that if I built the same wall, 5 bricks long and
12 courses high, but English bond, I'd use 86 bricks. Or, Flemish bond,
77 bricks.

But, if I use less bricks, because I choose Flemish over English bond,
say, I must use more mortar. That's what I think is the case. If mortar
is more expensive than brick, it would be more expensive to build with
less bricks.

Or, am I making a mistake somewhere?