It would be a good thing to take cheap displays, make a USB to SPI
convertor board, a bay mountable fixture possibly with buttons.
Overall cost budget should be pegged at $12-13 which is achievable.
Typical components and prices are LDO $1.5 ( 5V to 3.3V), a
microcontroller with a USB device (PIC or MSP $1.5) and board would
cost approx $1 with passives.
Yes. Sub $15 is my target too.