Expected fraction of satisfied constraints in formula F under bias b:
E(Z(F,b)) = SUMMATION ti * E(Z(Ri,b)),
where ti is the weighted ratio for relation Ri.
To find the break-even price, you solve:
min [t1, t2, ...] max [0<=b<=1]  E(Z(F,b))

There are several ways of doing this:

Symbolic closed form solution: compute maximum bias,
followed by computing the worst ti.
Tools from MathWorks or Mathematica would automate this.

Numerical, if only a small number of relations is involved.
Finds a good approximation, but the running time is 1000^(r+1)
where r is the number of relations. Assumes a fine grid of 1/1000.

Using linear programming by expressing the design of the symmetric
formula as a linear program. This requires finding a game inside the game,
as described here:

http://www.ccs.neu.edu/home/lieber/courses/csg113/f08/lectures/dec3/The%20Game%20Inside%20the%20Game.ppt

The linear programming approach is probably the easiest way to
approximate the break-even price of a derivative fairly well.
It is an approximation because the linear program has as many
columns as the symmetric formula has variables.