$1 substitute for a BEC

$1 car USB chargers were a good substitute for expensive voltage converters for many years. Just replace the feedback resistors with a pot & they could make any voltage at 1A.
Of course, if you didn't already have a bag of pots & caps, they would be a lot more than $1.

They were useless in their intended role as car chargers because the caps exploded in the heat.

The party ended when the Chinese finally moved to fixed voltage regulators. Any application would need to run on 5V now.