So I guess a gadget like this is worth 10$ because you could replace that linear breadboard power supply with a more efficient one, which will give you voltage and current display as well as adjustable output.
Here are some images I took during the teardown of the mini power supply:
Checkout this power supply from the links below:
60W Electronic Dummy Load Battery Tester:
A list of the items I show on this InTheMail video:
2.4 inch 320×240 px TFT display module based on the ILI9341 lcd controller, complete with touchscreen, uSD card slot, 128Mbit flash, independent font chip and the required power circuitry.
ESP8266 modules (3 different variations), a small solar panel, waterproof enclosure and Li-ion battery cells. uSD card holder thing. 13W LED 5050 E27 lightbulb. Breadboad + breadboard power supply + jumper cables. 0-30V 0-2A Adjustable lab power supply kit, unassembled. A bunch of components I ordered from Comet Electronics.