How do cheap power-supplies work?
However, when I went to price transformers, I quickly discovered that to buy a power transformer rated to hook into 110V AC, the transformer alone would always cost significantly more than the cost of buying a full ready-made power supply of similar output.
You can't buy a transformer rated for 110V for under $20-30, but you can find thousands of cheap wall-warts (transformer plus AD/DC conversion circuitry, plus connectors) for <<<$10. Or, if you look at higher wattage units, you find similarly rated (for volts and amps) power transformers cost $30-100+ dollars more than full power supplies.
How are these cheap power supplies made for the prices they are sold at? What am I missing here?