Build your own dance pads
Build Your Own
This is the cheapest of all methods. The cheapest design, in fact, is a more reliable design than a soft pad. But the construction process takes patience, tools for cutting and soldering, and the skill to use said tools. Many home-pad designs are meant for the Playstation 2, so they use the control box from an old soft pad and then run that through an adapter for Stepmania use. However, one possible USB substitute would be the I-PAC, which costs about as much as an adapter and control box but is designed with convenience in mind; it uses a terminal so no careful soldering to contacts is required.
Another option would be using the computer parallel port to input the panel switch data, which would work with any homemade pad, removing the need of buying an USB controller and soldering the pad switches there, further lowering the hardware cost. Obviously this limits the data input to 8 bits (ie, two 4-arrow pads or one 8-arrow pad). This can be achieved using a modified db9 driver (linux only), which adds a new device with 8 buttons and no axis.
"Pizo-Pad" (parts ~$5 and up)
The "Pizo-Pad" design involves the use of aluminum foil tape, available from most hardware stores. The foil tape is placed on the ground(or any desired surface) in patterns that easily allow a circuit to be completed on each panel; then when you play, you place some of the foil tape on your shoes, so that you become the switch triggering each arrow. The original design connects to a joystick port, but unfortunately these are increasingly uncommon in modern systems.
Wood/Metal Pad (parts ~$50? and up)
There are several example designs using wood and metal floating around the Internet. The general principle behind them, which is shared by most commercial pads, is that panels(usually made of tough acrylic) are laid on top of the sensor mechanism, and a connection is established via pressure. Arcade pads use some fairly expensive sensors on each side of each panel, fitting them in a pit built into the stage. Home pads have come up with cheaper ways to build a sensor; most are variations on the "pits-in-the-stage" concept with a cheaper switching mechanism, but the design used in Cobalt Flux pads is unusual: a flat base, with a gap between two metal plates established via velcro on each corner, and the decoration and clear lexan screwed in on top.
"Duelo de Bailes" Wood/Soft Pad with modified gamepad (parts ~$40 os less)
The "Duelo de Bailes" project is a middle range of homemade dancepad and well balanced choice between cost and quality. The main idea of this project is to use the cheapest gamepad and to take out its connections to plug them into the homemade dancepad. This alternative doesn't use expensive adapters or sensors, or materials such as metal or acrylic, but it has some features that others don't have. For example, it has a solid wood base, with a soft touch layer that can be folded to be stored.