That's an argument you could make about any corporate tax. For certain products (undifferentiated commodities with low profit margin) it's probably true. For some products, it's really up to the individual corporation how they deal with cost increases.

When the costs of producing/selling some goods go down, I don't expect most corporations to immediately lower prices, I expect them to use lower costs to increase their profits if they can get away with it. I imagine it goes the other way sometimes as well, especially if customers expect to pay no more than a certain price.