Not enough. I've been consistently stating throughout this thread that people need to pay for their use. The fact that motorists shoulder some but not all of the cost is not an argument that cyclists should be exempted from paying any of the cost.
None of what you're saying matters even a little bit if you're not able to provide any numbers on how much you're actually paying. Because we both know it's not 100%, or even 25%. So stop bullshitting.