True, but meaningless. Externalities cause
overconsumption because the product is cheaper than it should be. That overconsumption will cause problems down the line that may eventually harm the economy, so it is (
literally!) not healthy.
This is not entirely true, nor is it necessarily a problem. If a product is being overconsumed because it is too cheap, purchasing less may be better for them. If the price of a product increases it provides an incentive to produce alternatives that are cheaper - perhaps even becoming cheaper than the original ever was. What this means is that a market is most efficient when all the costs are internalized, even if it causes some products to become too expensive for people to purchase. When a market is working most efficiently it is using the least resources and producing the best overall value.
The problem with fossil fuels is that they were so cheap and abundant that they have become the basis of our economy, disincentivising the development of alternative energy sources. But now we realize that they have a hidden cost which has been piling up - and the Earth is demanding payment. So prices
will go up, but only until they reach the prices of alternative technologies - which will then become cheaper. Some renewables are already cheaper than coal, so in time they will push it out of the marketplace and
reduce energy costs in the long run. Considering that this occurred
without coal being made to pay for all its externalities, just imagine where we would be now if it was!
If only we hadn't been able to switch to coal (and then oil) when the
wood ran out, we might have solved this problem a lot earlier.