I was quoted $1,500.00 for parts, labor, and initial salt setup. To figure payback on chlorine only (in months), you would take the initial cost and divide it by the average $ amount you currently spend on chlorine each month. But...
...There are other factors you need to figure in your payback analysis such as periodic salt additions (will not be as frequent as manual chlorine additions), increased electrical usage of the SWG, and cell replacements about every 3-5 years. In addition, extremely hot weather, pool parties, and major storms may require that you manually add some chlorine to supplement the chlorine produced by the SWG. With Atlanta having a similar winter climate as Dallas, you may keep your pool operational year-round. If so, you need to factor in that the SWG is very inefficient when the water is cold. In fact, many SWGs shut down at cold temperatures. Therefore, you will need to revert to manual chlorine dosing during the winter. Granted, chlorine demand will drop in colder temperatures so you will not use as much chlorine in the winter as you do in summer. As you can see, a true payback analysis can get complex and the results obtained are only as good as the accuracy of the inputs.
As Leebo stated, the main benefit of a SWG is the ease of maintenance with regard to chlorine levels, not necessarily cost savings. If you travel frequently and the pool is routinely left unattended for significant periods of time (especially during the summer), a SWG makes good sense in that situation. It did not make sense for me since someone is always here and the pool is rarely left unattended even when we go on vacation.