How to calculate the intersection non linear aggregated curves

What I see:

A) Both curves are "step" functions -- curves that are flat for a span, then increase/decrease in steps. Most algorithms at my disposal do not like step functions.
B) However, both curves increase or decrease, so there are not multiple intersections.

My older copy of Solver does not have a good algorithm for this. My first thought, if your newer version of Solver (probably with the Evolutionary algorithm) can handle the "step" nature of the function, I would try something like Solver first.

1) Guess a price.
2) Use two lookup functions (approximate match option) to return the volume from each curve associated with that price.
3) Add a cell to compute the difference or the absolute value of the difference or the difference squared.
4) Call Solver and tell it to minimize the difference or find the closest value to 0 or similar.
5) See what solution Solver converges on and evaluate the result.

That's probably where I would start, if I had your newer version of Excel. Does that work for you?