> To me it matters a lot. Capitalism only works when the true costs of things are accurately reflected in their prices.

That's actually not true. Capitalism always works, no matter the problem. However, free markets don't account for externalities, and in some cases supply/demand constraints create unacceptable non-economic problems. Thus, to avoid the effects of non-economical problems then it's preferable to create economic incentives that reflect the non-economic constraints.