No, no, no, RL...
You see, its like a little kid's street lemonade stand. If the price is too high, another kid will open his stand across the street and charge less, and put the overpriced kid out of business.
You're right. "Extra" profit NEVER goes to reducing costs. It goes to increasing profits.
And lowering taxes will not go into increasing investment in new jobs. It goes to increasing profits.
The only thing that will lower prices is decreasing profit. It doesn't always work, but its always guaranteed to get their attention.