Regrettably they didn't crunch the numbers to produce the most useful one: an estimated value per bat. Someone did that with bees once, when trying to convince farmers not to spray all the bees to death. The campaign included the memorable line, "Whenever you see a bee, just think of her as a little $20 bill flying by." That helped.
Don't think plummeting bat populations are your problem? Bats eat insects including the mosquitoes that spread all those lovely tropical diseases that are spreading north, such as West Nile virus. Fewer bats mean more mosquitoes and a higher chance of getting bitten.