The price range on a hydroponic system can vary so much it's quite shocking. You can get a smaller system for as little as $80-90, whereas some indoor hydroponic grow box systems can go up to around $3,000! The difference is not always justifiable and unless money is really not an issue for you, I would recommend against buying such an expensive system, only to gain a few more millimeters in your plant's height. But if you're really looking for a wider range of products at such a huge price gap, try out Kalyx.com.
You might be tempted to buy a hydroponics system that's more expensive, because you'll think it gives you a better environment to grow your plants in. Although that might be the case sometimes, it's not a general rule. A lot of plants that do very well in a particular system will not have a spectacular growth in another one, despite the latter being more expensive. For example, strawberries, who are very keen on large amounts of water, will do better in an ebb and flow system than they will in an aeroponic one. You should first find the type of system that suits the plant you're growing best, then go for a store that gives you several options to choose from, such as the above mentioned Kalyx.com.
Also pay attention to the grow lights that come with your hydroponics system buy. Sometimes it's the lights that make up most of the price and in order to cut down costs, companies sell poor systems with good lights, boasting on the back of the quality lighting system to make you overlook the shortcomings of the system itself. If you have an option, I would say you're better off buying the hydroponic grow light system separately. If possible, try getting a lighting fixture that allows you to operate both a metal halide lamp and a high pressure sodium one. Metal halide lamps are great for the growing period of the plant whereas high pressure sodium is best during the plant's flowering. A system that allows you to switch between these two types of lights when needed is incredibly effective, although they usually come at a higher price. A great site offering hydroponic lights is Kalyx.com

It's often difficult to make the best hydroponics system buy because there are far more products out there than we can handle reviewing. Getting the right system depends on several factors and I'm going to try and help you out in making your choice in the following hydroponics system buy guide.