Have you really considered all the benefits individuals get from smoking? It makes them less nervous, more pleasant to be around (as long as they aren't smoking at that particular moment), and helps keep them thinner which reduces the costs of obesity. It also looks cool, and makes them cooler, and therefore improves the tone of the surroundings. And they carry lighters or matches, so in case of emergency power failures they are able to quickly produce light.
Life is for enjoying, and people should be able to enjoy whatever they wish as long as it isn't harming anyone else. "Economic costs" isn't really a harm to you--unless you are in perfect health yourself, you are costing them money as well. You can't possibly calculate all the numbers and variables that would be involved in proving that smoking causes economic harm to the general public. In fact, in many areas (such as my own employment) it's decidedly beneficial.