Aeroponics systems can range from $100 to $1000 or more, depending on your style, and whether you're purchasing a full setup or designing a DIY project. In general, low pressure aquaponics (LPA) systems are the least expensive, since the pump and nozzles are less expensive, while high pressure (HPA) and fogponics systems are considerably more complex and require more equipment
Basic LPA systems are available in garden stores and online for very low prices if DIY isn't your style. You'll probably be limited in how many plants you can support, but it's not a bad way to get a taste of what you're getting into. DIY HPA systems, which are basically a set of components which you assemble yourself, can be found in the $300-$500 range, but again, the number of plants will be limited. Larger or custom designed systems will increase in price with the size of the pump, the cost of extra tubing and nozzles, etc.
