The elasticity of the cost of capital is base on interest rates, the state of the equity markets, a company's credit rating and outlook etc. The cost of capital, like the cost of taxes has nothing to do with what a company is able to charge for its goods and services. Please don't confuse liberals with economics. Of course, how much tax is passed on is a function of the elasticity of supply, as well as the elasticity of demand.
Here is a bit more on who pays the corporate income tax. The guy
here states that the current thinking is that it is mostly a disguised sales tax, which assumes a high elasticity of supply of capital on an after tax basis.